Electrical power saving system

ABSTRACT

An electrical power saving system including a video display apparatus and at least two video and audio signal transmission apparatuses connected to each other via a communication network. Each of the video and audio signal transmission apparatuses includes a transmission and reception unit that transmits and receives a control command via the communication network and an operation state switching unit that switches an operation state according to the control command. The operation state switching unit is configured to switch a current operation state to an operation state of lower electricity consumption, when the transmission and reception unit receives a control command indicating that another video and audio signal transmission apparatus is transmitting a video and audio signal to the video display apparatus.

This application is a divisional application of application Ser. No.12/866,967, which is the National Stage of International Application No.PCT/JP2009/000550, filed Feb. 12, 2009.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to an electrical power saving system, andparticularly relates to an AV system and an AV apparatus control methodin which electricity consumption of the system is controlled byswitching operation modes of apparatuses connected via a communicationnetwork.

2. Description of Related Art

Conventionally, there is an Audio/Visual (AV) system in which a videorecording and reproduction apparatus such as a Digital Versatile Disc(DVD) recorder is connected to a television receiver (hereafter referredto as “TV”). In the AV system, video and audio are viewed, and anexternal AV amplifier and an external speaker are further connected tooutput audio from the external speaker. In order to view and operateeach apparatus in such an AV system, the user needs to perform anoperation of input selection or reproduction by separately using aremote controller (hereafter referred to as “remote control”)corresponding to the apparatus. This requires a complex operation.

One method for solving this problem is a method that employs aHigh-Definition Multimedia Interface (HDMI) standard. In HDMI, a featurenamed Consumer Electronics Control (CEC) is defined (Non-patentReference 1). CEC is a feature that connects a TV and various AVapparatuses by HDMI cables, and controls the AV apparatuses using CECcommands which enable bidirectional control command transmission andreception, via CEC buses included in the HDMI cables.

Moreover, the HDMI standard has a feature that a reproduction apparatussuch as a DVD recorder can read reproduction capability information of aconnected apparatus to adapt video and audio data to an output format ofthe connected apparatus or encrypt the video and audio data, andtransmit the video and audio data.

For example, reproduction capability information is transferred from anapparatus (hereafter referred to as “HDMI input apparatus”) including aHDMI input unit, such as a TV or an AV amplifier, to an apparatus(hereafter referred to as “HDMI output apparatus”) to which the HDMIinput apparatus is connected, using a Display Data Channel (DDC) busthat is a unidirectional connection. “DDC” mentioned here is a standardcreated by the Video Electronics Standards Association (VESA) as afeature of communicating model information and the like of a display tothe HDMI output apparatus, in order to achieve plug and play for thedisplay. Information transferred by DDC includes model information and areproducible image and audio format of the HDMI input apparatus, aphysical address assigned to the HDMI apparatus, and so on.

In the HDMI standard, a logical address (hereafter “LA”) and a physicaladdress (hereafter “PA”) are defined for each apparatus, forcommunication by CEC commands.

A PA is an address determined so as to reflect a connection topology ofthe HDMI output apparatus, and is unidirectionally transmitted from theHDMI input apparatus to the HDMI output apparatus. The PA is determinedby adding a value that differs for each HDMI input unit, to a PAobtained by the HDMI input apparatus.

An apparatus that includes both a HDMI input unit and a HDMI outputunit, such as an AV amplifier, obtains a PA of the AV amplifier itselffrom an apparatus to which the HDMI output unit is connected. The AVamplifier then adds a value corresponding to the HDMI input unit to theobtained PA, thereby determining a PA of a HDMI output apparatusconnected to the AV amplifier. Accordingly, a PA of an apparatus(hereafter “root apparatus”) that includes a HDMI input unit and servesas a root is determined hierarchically as “0. 0. 0. 0”.

For instance, a TV that includes no HDMI output unit and only includes aHDMI input unit always has the PA “0. 0. 0. 0”, as a root apparatus. APA of an apparatus connected to the root apparatus is determined in sucha manner that, as an example, a PA of an apparatus connected to a firstHDMI input unit of the root apparatus is “1. 0. 0. 0” and a PA of anapparatus connected to a second HDMI input unit of the root apparatus is“2. 0. 0. 0”.

An apparatus that includes both an input unit and an output unit furtherdetermines a PA for each input unit, from a PA of the apparatus itself.As an example, a PA of an apparatus connected to a first input unit ofthe apparatus having the PA “1. 0. 0. 0” is “1. 1. 0. 0”, and a PA of anapparatus connected to a second input unit of the apparatus having thePA “1. 0. 0. 0” is “1. 2. 0. 0”.

On the other hand, a LA is assigned to each CEC-capable apparatusconnected via HDMI, and used as a destination address for CEC commandtransmission and reception.

In CEC, there are a command that is transmitted to a designateddestination, and a broadcast command that is notified to all CEC-capableapparatuses connected via HDMI. Communication is performed by combiningthese commands in CEC.

Note that a CEC command is made up of a LA of a transmitter apparatus, aLA of a destination apparatus, an opcode, and an operand.

Furthermore, HDMI defines control commands such as <Active Source> forperforming input selection, <Standby> for powering OFF an apparatus,<Give Power Status> for querying a power state of an apparatus, <PollingMessage> for ascertaining whether or not an apparatus of a destinationLA is present on a communication network, and <Vendor Command> enablingeach manufacturer to independently define an apparatus operation. InHDMI, various cooperative operations can be realized by transmitting andreceiving these control commands in combination between CEC-capableapparatuses connected via HDMI.

Non-patent Reference 1: High-Definition Multimedia InterfaceSpecification Version 1.3a

SUMMARY OF THE INVENTION 1. Problems that Invention is to Solve

In CEC, the <Standby> command is defined as a command for powering OFF aconnected apparatus, An apparatus such as a DVD recorder has a pluralityof operation states even in a power-OFF state. These operation statesdiffer in electricity consumption.

In conventional techniques, however, it is impossible to control theplurality of operation states in the connected apparatus. This causesinefficient consumption of electricity as in the case where, even whenthe user is not using an apparatus, a function in the apparatus isenergized. In order to improve electricity consumption efficiency by auser operation, the user needs to switch the operation state of eachconnected apparatus by operating a button or a remote control of theapparatus. This requires a complex operation for the user.

Besides, in order to check an amount of electricity consumption of theapparatus, the user needs to newly connect a watt-hour meter or the likeand perform measurement. Thus, a complex operation is needed forimproving electricity consumption efficiency.

The present invention has been made in view of the above problems, andhas an object of realizing an electrical power saving system thatachieves efficient electricity consumption of apparatuses connected viaa communication network.

2. Means to Solve the Problems

To solve the above problems, an electrical power saving system accordingto the present invention is an electrical power saving system includingat least a first apparatus and a second apparatus that are connected toeach other via a communication network, each of the first apparatus andthe second apparatus including: a transmission and reception unit thattransmits and receives a control command via the communication network,the control command being a command by which one apparatus controlsanother apparatus; and an operation state switching unit that switchesan operation state according to the control command, wherein each of thefirst apparatus and the second apparatus has at least a first OFFoperation mode and a second OFF operation mode as operation states thatdiffer in electricity consumption, the first OFF operation mode being anoperation state in which the apparatus is in a power-OFF state but apart of the apparatus is supplied with power, and the second OFFoperation mode being an operation state of lower electricity consumptionthan the first OFF operation mode, and the operation state switchingunit in the second apparatus switches the operation state of the secondapparatus from the first OFF operation mode to the second OFF operationmode in the case where, when the second apparatus is in the first OFFoperation mode, the transmission and reception unit in the secondapparatus receives a control command instructing to switch the operationstate, from the first apparatus.

In this way, an operation state of a connected apparatus can be switchedby a control command of another apparatus and the like. Hence, in asystem where a plurality of apparatuses that each have a plurality ofoperation states of different electricity consumption are connected viaa communication network such as HDMI, the operation state of theplurality of apparatuses can be controlled so as to improve electricityconsumption efficiency. This makes it possible to realize an electricalpower saving system that achieves efficient electricity consumption ofapparatuses connected via a communication network.

Preferably, the second apparatus further includes a timer unit thatcounts an elapse of a predetermined time, wherein the operation stateswitching unit in the second apparatus switches the operation state ofthe second apparatus from the first OFF operation mode to the second OFFoperation mode, when the timer unit counts the elapse of thepredetermined time during which the second apparatus is in the first OFFoperation mode. Here, the second apparatus may further include adetermination unit that determines the operation state of the firstapparatus according to the control command transmitted and received bythe transmission and reception unit in the second apparatus, wherein thetransmission and reception unit in the first apparatus transmits, as thecontrol command, a control command including the operation state of thefirst apparatus, to the second apparatus, and the operation stateswitching unit in the second apparatus switches the operation state ofthe second apparatus from the first OFF operation mode to the second OFFoperation mode in the case where, when the second apparatus is in thefirst OFF operation mode, the determination unit determines that thefirst apparatus is in an operation state in which the first apparatus isin a power-OFF state, the operation state in which the first apparatusis in a power-OFF state including the first OFF operation mode and thesecond OFF operation mode.

In this way, the operation state of the apparatus can be switched notonly by the control command of another apparatus, but also by using theelapse of the time set in the apparatus or the state of anotherapparatus as a trigger.

Moreover, to solve the above problems, an electrical power saving systemaccording to the present invention is an electrical power saving systemincluding at least a video display apparatus and a video recordingapparatus that are connected to each other via a communication network,each of the video display apparatus and the video recording apparatusincluding: a transmission and reception unit that transmits and receivesa control command via the communication network, the control commandbeing a command by which one apparatus controls another apparatus; andan operation state switching unit that switches an operation stateaccording to the control command, wherein each of the video displayapparatus and the video recording apparatus has at least a first OFFoperation mode and a second OFF operation mode as operation states thatdiffer in electricity consumption, the first OFF operation mode being anoperation state in which the apparatus is in a power-OFF state but apart of the apparatus is supplied with power, and the second OFFoperation mode being an operation state of lower electricity consumptionthan the first OFF operation mode, and the operation state switchingunit in the video recording apparatus switches the operation state ofthe video recording apparatus from the first OFF operation mode to thesecond OFF operation mode in the case where, when the video recordingapparatus is in the first OFF operation mode, the transmission andreception unit in the video recording apparatus receives a controlcommand instructing to switch the operation state, from the videodisplay apparatus.

Note that the present invention can be realized not only as a system,but also as an apparatus or an integrated circuit including processingunits of the system, or a method including steps that correspond to theprocessing units of the system.

3. Effects of the Invention

According to the present invention, it is possible to realize anelectrical power saving system that achieves efficient electricityconsumption of connected apparatuses.

In detail, by switching an operation state of a connected apparatus by asimple user operation and the like so as not to energize an unusedfunction, an electrical power saving system that achieves efficientelectricity consumption of apparatuses connected via a communicationnetwork can be realized.

Moreover, there is also an advantageous effect that the user can checkan amount of electricity consumption measured without connecting a newapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural diagram of an AV system in a first embodiment ofthe present invention.

FIG. 2 is a functional block diagram of a TV 10 in the first embodimentof the present invention.

FIG. 3 is a functional block diagram of a DVD recorder 20 in the firstembodiment of the present invention.

FIG. 4 is a functional block diagram of a set-top box 30 in the firstembodiment of the present invention.

FIG. 5A is a diagram showing a correspondence table of operation modesand functions in the DVD recorder 20 in the first embodiment of thepresent invention.

FIG. 5B is a diagram showing a correspondence table of operation modesand functions in the set-top box 30 in the first embodiment of thepresent invention.

FIG. 5C is a diagram showing a correspondence table of operation modesand functions in the TV 10 in the first embodiment of the presentinvention.

FIG. 6 is a diagram showing an example of a menu for setting anoperation mode and a function in the DVD recorder 20 in the firstembodiment of the present invention.

FIG. 7 is a diagram showing an example of an operation mode switchingtime setting method by an OSD menu display in the TV 10 in the firstembodiment of the present invention.

FIG. 8 is a diagram showing an example of a mode switching time settingtable in the TV 10 in the first embodiment of the present invention.

FIG. 9 is a diagram showing an example of a flow of CEC commandtransmission and reception when the DVD recorder 20 and the set-top box30 operate according to a user operation in the first embodiment of thepresent invention.

FIG. 10 is a diagram showing an example of correspondence of operationstates and electricity consumption in the DVD recorder 20 in the firstembodiment of the present invention.

FIG. 11 is a diagram showing an example of changes in operation andelectricity consumption of the DVD recorder 20 in the first embodimentof the present invention.

FIG. 12 is a diagram showing an example of displaying an operation stateof each apparatus and a total amount of electricity consumption in theAV system, in the TV 10 in the first embodiment of the presentinvention.

FIG. 13 is a structural diagram of an AV system in a second embodimentof the present invention.

FIG. 14 is a functional block diagram of a TV 50 in the secondembodiment of the present invention.

FIG. 15 is a functional block diagram of a DVD recorder 60 in the secondembodiment of the present invention.

FIG. 16 is a functional block diagram of a set-top box 70 in the secondembodiment of the present invention.

FIG. 17 is a diagram showing an example of an OSD menu for setting afunction that is operational in an operation mode 3 and switching to theoperation mode 3, in the TV 50 in the second embodiment of the presentinvention.

FIG. 18 is a diagram showing an example of a flow of CEC commandtransmission and reception when the DVD recorder 60 and the set-top box70 operate according to a user operation in the second embodiment of thepresent invention.

FIG. 19 is a diagram: showing an example of an OSD display for notifyingthe user of power OFF, in the TV 50 in the second embodiment of thepresent invention.

FIG. 20 is a diagram: showing an example of an OSD display for notifyingthe user of an amount of saved electricity consumption, in the TV 50 inthe second embodiment of the present invention.

FIG. 21 is a structural diagram of an AV system including an AVamplifier 65.

FIG. 22 is a diagram showing an example of a correspondence table ofoperation modes and functions in the AV amplifier 65.

NUMERICAL REFERENCES

-   -   10, 50 TV    -   20, 60 DVD recorder    -   30, 70 Set-top box    -   40 Remote control    -   65 AV amplifier    -   101, 201, 301, 501 Operation mode switching timer    -   102, 202, 302, 502 Electricity consumption amount storage unit    -   103, 203, 303, 503 Saved electricity consumption amount storage        unit    -   104, 204, 304 Electricity consumption storage unit    -   105, 205, 305 Remote control reception unit    -   106 Video output unit    -   107 Audio output unit    -   108 Active source apparatus storage unit    -   208, 308 Active source state storage unit    -   109 Connected apparatus list storage unit    -   110, 210, 310, 510, 610, 710 Microcomputer    -   111, 211, 311, 511, 611, 711 CEC communication unit    -   112 TMDS decoding unit    -   212, 312 Decoding unit    -   113 TMDS input unit    -   114, 115 HDMI input unit    -   214, 314 HDMI output unit    -   120, 220, 320 Tuner    -   121, 221, 321 Operation function setting storage unit    -   122, 222, 322 Operation state storage unit    -   216, 316 TV power state determination unit    -   217 Recording timer    -   218 IP communication unit    -   219 Recording unit

DETAILED DESCRIPTION OF THE INVENTION

The following describes embodiments of an AV system and an AV apparatuscontrol method according to the present invention in detail, withreference to drawings.

First Embodiment Structure

FIG. 1 is a diagram schematically showing a structure of an AV system ina first embodiment. FIG. 2 is a functional block diagram of a TV 10 inthe first embodiment. FIG. 3 is a functional block diagram of a DVDrecorder 20 in the first embodiment. FIG. 4 is a functional blockdiagram of a set-top box 30 in the first embodiment.

Note that the TV 10 in the first embodiment is an example of a firstapparatus according to the present invention, and each of the DVDrecorder 20 and the set-top box 30 in the first embodiment is an exampleof a second apparatus according to the present invention.

As shown in FIG. 1, the AV system in the first embodiment includes theTV 10, the DVD recorder 20, and the set-top box 30. The AV system alsoincludes, for example, a remote control 40.

In the AV system, the DVD recorder 20 and the set-top box 30 areconnected to the TV 10 via HDMI cables. CEC lines in HDMI are connectedin a CEC communication unit 111 in the TV 10. The TV 10, the DVDrecorder 20, and the set-top box 30 are capable of performingtransmission and reception of a CEC command as a control command witheach other.

The TV 10 is an apparatus that outputs video and audio outputted from anapparatus connected via a HDMI cable, and a broadcast signal receivedvia an antenna (not shown).

The TV 10 includes an operation mode switching timer 101, an electricityconsumption amount storage unit 102, a saved electricity consumptionamount storage unit 103, an electricity consumption storage unit 104, aremote control reception unit 105, a video output unit 106, an audiooutput unit 107, an active source apparatus storage unit 108, aconnected apparatus list storage unit 109, a microcomputer 110, the CECcommunication unit 111, a TMDS decoding unit 112, a TMDS input unit 113,HDMI input units 114 and 115, a tuner 120, an operation function settingstorage unit 121, and an operation state storage unit 122.

The operation mode switching timer 101 includes a timer and an operationmode switching time storage unit.

The operation mode switching timer 101 stores a time 1 to switch to anoperation mode 1 and a time 2 to switch to an operation mode 2, via themicrocomputer 110. When the time 1 or the time 2 is reached, theoperation mode switching timer 101 notifies the microcomputer 110 thatthe corresponding set time is reached.

The electricity consumption amount storage unit 102 includes acurrent-day storage unit that temporarily stores an amount ofelectricity consumption of a current day, and a log recording unit thatstores an amount of electricity consumption of a past fixed time period.Note that the log recording unit in the electricity consumption amountstorage unit 102 is composed of a nonvolatile storage device.

The saved electricity consumption amount storage unit 103 includes acurrent-day storage unit that temporarily stores an amount of savedelectricity consumption of the current day, and a log recording unitthat stores an amount of saved electricity consumption of the past fixedtime period. Note that the log recording unit in the saved electricityconsumption amount storage unit 103 is composed of a nonvolatile storagedevice.

The electricity consumption storage unit 104 stores electricityconsumption in each of a plurality of operation states of the TV 10.

The remote control reception unit 105 receives a signal transmitted fromthe remote control 40, and notifies the microcomputer 110 of the signal.Here, as an input unit, the remote control 40 includes a plurality ofbuttons such as a power button, a menu display button, and up, down,left, and right buttons, and a remote control signal transmission unit.

The video output unit 106 is a display unit, and displays videooutputted from the TMDS decoding unit 112 or the tuner 120. The videooutput unit 106 also performs On Screen Display (OSD) by superimposing amessage and a menu on input video, according to a notification from themicrocomputer 110.

The audio output unit 107 is a speaker unit, and outputs audio outputtedfrom the TMDS decoding unit 112 or the tuner 120.

The active source apparatus storage unit 108 stores, when the CECcommunication unit 111 receives an <Active Source> command from anotherapparatus, a LA and a PA of the apparatus transmitting the command. Whenthe CEC communication unit 111 transmits an <Active Source> command, onthe other hand, the active source apparatus storage unit 108 storesinformation that the TV 10 is an active source.

The connected apparatus list storage unit 109 receives a response to a<Polling Message> command transmitted by the CEC communication unit 111and a command from another apparatus, and stores a list of apparatusesconnected to the communication network.

The microcomputer 110 is a device that executes a program. Themicrocomputer 110 receives a notification from any of the operation modeswitching timer 101, the remote control reception unit 105, and the CECcommunication unit 111. Upon receiving the notification, themicrocomputer 110 reads or writes information in each storage unit suchas the electricity consumption amount storage unit 102, the savedelectricity consumption amount storage unit 103, the electricityconsumption storage unit 104, the active source apparatus storage unit108, the connected apparatus list storage unit 109, the operationfunction setting storage unit 121, and the operation mode switchingtimer 101, and also controls the CEC communication unit 111, the tuner120, the video output unit 106, and the like. The microcomputer 110 alsocontrols various functions of the TV 10 not shown.

The CEC communication unit 111 is an example of a device that transmitsand receives a control command via the communication network. The CECcommunication unit 111 performs transmission and reception of a CECcommand.

The HDMI input unit 114 is a HDMI input port. In this embodiment, theHDMI input unit 114 is HDMI-connected with the DVD recorder 20, andperforms reception of video and audio data and bidirectionalcommunication of a control message. The HDMI input unit 114 is used fortransmission of a HPD signal 114_1, a DDC signal 114_2, a TMDS signal114_3, and a CEC signal 114_4.

The HDMI input unit 115 is a HDMI input port. In this embodiment, theHDMI input unit 115 is HDMI-connected with the set-top box 30, andperforms reception of video and audio data and bidirectionalcommunication of a control message. The HDMI input unit 115 is used fortransmission of a HPD signal 115_1, a DDC signal 115_2, a TMDS signal115_3, and a CEC signal 115_4.

Here, the HDMI input units 114 and 115 are not limited to HDMI. Forinstance, the HDMI input units 114 and 115 may each be an interfacecorresponding to an adapted communication mode or the like that providesthe function described above, regardless of whether it is wired orwireless.

The TMDS input unit 113 receives TMDS data using the TMDS signal 114_3or 115_3 of the HDMI input unit 114 or 115, and outputs the TMDS data tothe TMDS decoding unit 112.

The TMDS decoding unit 112 TMDS-decodes the TMDS data, and outputsdecoded video data to the video output unit 106 and decoded audio datato the audio output unit 107.

The tuner 120 decodes a broadcast signal received via an antenna (notshown). The tuner 120 outputs decoded video data to the video outputunit 106, and decoded audio data to the audio output unit 107.

The operation function setting storage unit 121 stores a table showingcorrespondence between various operation states and various functions ofthe TV 10, as shown in FIG. 5C. Note that the functions of the TV 10shown in FIG. 5C are merely an example, and the present invention is notlimited to these functions, so long as all functions of the TV 10 areassociated with operation states.

The operation state storage unit 122 is a storage device. When the TV 10changes in operation state, the operation state storage unit 122 storesa start time of the operation state and information showing theoperation state. The operation state storage unit 122 also stores a flagshowing whether or not the state change to the operation state is causedby the operation mode switching timer 101. The operation state storageunit 122 further stores information that the operation state continues,in an operation duration time storage unit at predetermined timeintervals.

The DVD recorder 20 is an apparatus that records a broadcast signalreceived via an antenna (not shown), and outputs a recorded video andaudio signal via a HDMI cable. As shown in FIG. 3, the DVD recorder 20includes an operation mode switching timer 201, an electricityconsumption amount storage unit 202, a saved electricity consumptionamount storage unit 203, an electricity consumption storage unit 204, aremote control reception unit 205, an active source state storage unit208, a microcomputer 210, a CEC communication unit 211, a decoding unit212, a TMDS output unit 213, a HDMI output unit 214, a TV power statedetermination unit 216, a recording timer 217, an IP communication unit218, a recording unit 219, a tuner 220, an operation function settingstorage unit 221, and an operation state storage unit 222.

The operation mode switching timer 201 includes a timer and an operationmode switching time storage unit. The operation mode switching timer 201stores the time 1 to switch to the operation mode 1 and the time 2 toswitch to the operation mode 2, via the microcomputer 210. When the time1 or the time 2 is reached, the operation mode switching timer 201notifies the microcomputer 210 that the corresponding set time isreached.

The electricity consumption amount storage unit 202 includes acurrent-day storage unit that temporarily stores an amount ofelectricity consumption of the current day, and a log recording unitthat stores an amount of electricity consumption of the past fixed timeperiod. Note that the log recording unit in the electricity consumptionamount storage unit 202 is composed of a nonvolatile storage device.

The saved electricity consumption amount storage unit 203 includes acurrent-day storage unit that temporarily stores an amount of savedelectricity consumption of the current day, and a log recording unitthat stores an amount of saved electricity consumption of the past fixedtime period. Note that the log recording unit in the saved electricityconsumption amount storage unit 203 is composed of a nonvolatile storagedevice.

The electricity consumption storage unit 204 stores electricityconsumption in each of a plurality of operation states of the DVDrecorder 20.

The remote control reception unit 205 receives a signal transmitted fromthe remote control 40 (not shown) corresponding to the DVD recorder 20,and notifies the microcomputer 210 of the signal. Here, as mentionedearlier, the remote control 40 includes the plurality of buttons such asthe power button, the menu display button, and the up, down, left, andright buttons, and the remote control signal transmission unit, as theinput unit.

The active source state storage unit 208 stores information that the DVDrecorder 20 is an active source, when the CEC communication unit 211transmits an <Active Source> command. When the CEC communication unit211 receives an <Active Source> command from another apparatus, on theother hand, the active source state storage unit 208 deletes theinformation that the DVD recorder 20 is in an active source state.

The microcomputer 210 is a device that executes a program. Themicrocomputer 210 receives a notification from any of the operation modeswitching timer 201, the remote control reception unit 205, the CECcommunication unit 211, the TV power state determination unit 216, andthe recording timer 217. Upon receiving the notification, themicrocomputer 210 reads or writes information in each storage unit suchas the electricity consumption storage unit 204, the electricityconsumption amount storage unit 202, the saved electricity consumptionamount storage unit 203, the active source state storage unit 208, andthe operation function setting storage unit 221, and also controls theCEC communication unit 211, the decoding unit 212, the IP communicationunit 218, the recording unit 219, the tuner 220, and the like. Themicrocomputer 210 also controls other various functions of the DVDrecorder 20 not shown.

For example, the microcomputer 210 controls an IP communication unit (IPcommunication function) that communicates with another apparatus, and aLED clock display unit (LED clock display function) that displays acurrent time, received channel information, and the like. Themicrocomputer 210 also controls the recording unit 219 (recordingfunction) that records a broadcast signal (containing video and audiodata) outputted from the tuner. The microcomputer 210 can perform powerON/OFF control on each of these components individually.

The CEC communication unit 211 is an example of a device that transmitsand receives a control command via the communication network. The CECcommunication unit 211 performs transmission and reception of a CECcommand.

Note that the communication network for transmitting and receiving thecontrol command is not limited to CEC, and a wired or wireless networkof IP or the like may instead be used.

The decoding unit 212 appropriately decodes video and audio datareceived from the tuner 220 or the recording unit 219, and outputs thedecoded video data and audio data to the TMDS output unit 213.

The TMDS output unit 213 outputs the video data and the audio data via aTMDS signal 214_3 in the HDMI output unit 214, as a TMDS data signal.

The HDMI output unit 214 outputs the TMDS data received from the TMDSoutput unit 213, using the TMDS signal 214_3.

The TV power state determination unit 216 receives a CEC commandtransmitted from the TV 10 via the CEC communication unit 211, anddetermines whether the TV 10 is powered ON or OFF by querying a powerstate of the TV 10. The TV power state determination unit 216 notifiesthe microcomputer 210 of a result of the determination.

The recording timer 217 is a timer for starting programmed recording ofa broadcast. When a set time is reached, the recording timer 217notifies the recording unit 219 and the microcomputer 210 of therecording start.

The IP communication unit 218 is an example of a function of the DVDrecorder 20, and performs information transmission and reception with aconnected apparatus (not shown) by IP communication.

The recording unit 219 is a device that records a broadcast signaloutputted from the tuner 220, in a storage device such as a hard disk.

The tuner 220 outputs a broadcast signal received via an antenna (notshown), to the recording unit 219 or the decoding unit 212.

The operation function setting storage unit 221 stores a table showingcorrespondence between various operation states and various functions ofthe DVD recorder 20, as shown in FIG. 5A.

Note that the functions of the DVD recorder 20 shown in FIG. 5A aremerely an example, and the present invention is not limited to thesefunctions. All functions of the DVD recorder 20 are associated withoperation states.

The operation state storage unit 222 is a storage device. When the DVDrecorder 20 changes in operation state, the operation state storage unit222 stores a start time of the operation state and information showingthe operation state. The operation state storage unit 222 also stores aflag showing whether or not the state change to the operation state iscaused by the operation mode switching timer 201. The operation statestorage unit 222 further stores information that the operation statecontinues, in an operation duration time storage unit at predeterminedtime intervals.

The set-top box 30 is an apparatus that decodes a broadcast signalreceived via a broadcast signal cable (not shown), and outputs a videoand audio signal via a HDMI cable.

As shown in FIG. 4, the set-top box 30 includes an operation modeswitching timer 301, an electricity consumption amount storage unit 302,a saved electricity consumption amount storage unit 303, an electricityconsumption storage unit 304, a remote control reception unit 305, anactive source state storage unit 308, a microcomputer 310, a CECcommunication unit 311, a decoding unit 312, a TMDS output unit 313, aHDMI output unit 314, a TV power state determination unit 316, a tuner320, an operation function setting storage unit 321, and an operationstate storage unit 322.

The operation mode switching timer 301 includes a timer and an operationmode switching time storage unit. The operation mode switching timer 301stores the time 1 to switch to the operation mode 1 and the time 2 toswitch to the operation mode 2, via the microcomputer 310. When the time1 or the time 2 is reached, the operation mode switching timer 301notifies the microcomputer 310 that the corresponding set time isreached.

The electricity consumption amount storage unit 302 includes acurrent-day storage unit that temporarily stores an amount ofelectricity consumption of the current day, and a log recording unitthat stores an amount of electricity consumption of the past fixed timeperiod. Note that the log recording unit in the electricity consumptionamount storage unit 302 is composed of a nonvolatile storage device.

The saved electricity consumption amount storage unit 303 includes acurrent-day storage unit that temporarily stores an amount of savedelectricity consumption of the current day, and a log recording unitthat stores an amount of saved electricity consumption of the past fixedtime period. Note that the log recording unit in the saved electricityconsumption amount storage unit 303 is composed of a nonvolatile storagedevice.

The electricity consumption storage unit 304 stores electricityconsumption in each of a plurality of operation states of the set-topbox 30.

The remote control reception unit 305 receives a signal transmitted fromthe remote control 40 (not shown) corresponding to the DVD recorder 20,and notifies the microcomputer 310 of the signal. Here, as mentionedearlier, the remote control 40 includes the plurality of buttons such asthe power button, the menu display button, and the up, down, left, andright buttons, and the remote control signal transmission unit, as theinput unit.

The active source state storage unit 308 stores information that theset-top box 30 is an active source, when the CEC communication unit 311transmits an <Active Source> command. When the CEC communication unit311 receives an <Active Source> command from another apparatus, on theother hand, the active source state storage unit 308 deletes theinformation that the set-top box 30 is in an active source state.

The microcomputer 310 is a device that executes a program. Themicrocomputer 310 receives a notification from any of the operation modeswitching timer 301, the remote control reception unit 305, the CECcommunication unit 311, and the TV power state determination unit 316.Upon receiving the notification, the microcomputer 310 reads or writesinformation in each storage unit such as the electricity consumptionstorage unit 304, the electricity consumption amount storage unit 302,the saved electricity consumption amount storage unit 303, the activesource state storage unit 308, and the operation function settingstorage unit 321, and also controls the CEC communication unit 311, thedecoding unit 312, the tuner 320, and the like. The microcomputer 310also controls various functions of the set-top box 30 not shown.

The CEC communication unit 311 is an example of a device that transmitsand receives a control command via the communication network. The CECcommunication unit 311 performs transmission and reception of a CECcommand.

Note that the communication network for transmitting and receiving thecontrol command is not limited to CEC, and a wired or wireless networkof IP or the like may instead be used.

The decoding unit 312 appropriately decodes video and audio datareceived from the tuner 320, and outputs the decoded video data andaudio data to the TMDS output unit 313.

The TMDS output unit 313 outputs the video data and the audio data via aTMDS signal 314_3 in the HDMI output unit 314, as a TMDS data signal.

The HDMI output unit 314 outputs the TMDS data received from the TMDSoutput unit 313, using the TMDS signal 314_3.

The TV power state determination unit 316 receives a CEC commandtransmitted from the TV 10 via the CEC communication unit 311, anddetermines whether the TV 10 is powered ON or OFF by querying a powerstate of the TV 10. The TV power state determination unit 316 notifiesthe microcomputer 310 of a result of the determination.

The tuner 320 outputs a broadcast signal received via an antenna (notshown), to the recording unit 219 or the decoding unit 212.

The operation state storage unit 322 is a storage device. When theset-top box 30 changes in operation state, the operation state storageunit 322 stores a start time of the operation state and informationshowing the operation state.

The operation state storage unit 322 also stores a flag showing whetheror not the state change to the operation state is caused by theoperation mode switching timer 301. The operation state storage unit 322further stores information that the operation state continues, in anoperation duration time storage unit at predetermined time intervals.

The operation function setting storage unit 321 stores a table showingcorrespondence between various operation states and various functions ofthe set-top box 30, as shown in FIG. 5B.

Note that the functions of the set-top box 30 shown in FIG. 5B aremerely an example, and the present invention is not limited to thesefunctions, so long as all functions of the set-top box are associatedwith operation states.

<Operation>

(Setting of Operation Mode and Operational Function Combination by theUser)

The TV 10, the DVD recorder 20, and the set-top box 30 connected via thecommunication network store an operation mode and functioncorrespondence table showing a function that is operational in eachoperation mode, respectively in the operation function setting storageunits 121, 221, and 321.

FIGS. 5A, 5B, and 5C respectively show an example of the operation modeand function correspondence table in the DVD recorder 20, the set-topbox 30, and the TV 10. In FIGS. 5A, 5B, and 5C, each of the DVD recorder20, the set-top box 30, and the TV 10 has a plurality of operationmodes, in each of which a function is energized so as to be operationalor is not energized so as to be non-operational.

For example, in the DVD recorder 20, when the operation mode of the DVDrecorder 20 is a power-OFF operation mode 2 and also the TV power statedetermination unit 216 determines that the TV 10 is powered OFF, therecording function is operational but the IP communication function, theLED clock display function, and a HDMI video and audio output functionare non-operational, as shown in FIG. 5A.

Moreover, the DVD recorder 20 in a power-OFF state has at least apower-OFF operation mode 1 and the power-OFF operation mode 2 thatdiffer in electricity consumption, as shown in FIG. 5A. That is, the DVDrecorder 20 has, for example, the power-OFF operation mode 1 and thepower-OFF operation mode 2. The power-OFF operation mode 1 is a state inwhich the DVD recorder 20 is in a power-OFF state but a part of the DVDrecorder 20 is supplied with power, as in the case where the recordingfunction and a main microcomputer function including the IPcommunication function and the LED clock display function are energizedwhile the HDMI video and audio output function is not energized. Thepower-OFF operation mode 2 is a state in which the DVD recorder 20 is ina power-OFF state and fewer functions are operational than in thepower-OFF operation mode 1, as in the case where only the recordingfunction is energized while the HDMI video and audio output function andthe main microcomputer function are not energized. Thus, fewer functionsare energized in the power-OFF operation mode 2 than in the power-OFFoperation mode 1, and so the power-OFF operation mode 2 has lowerelectricity consumption than the power-OFF operation mode 1.

The DVD recorder 20 also has an operation mode 3 (full OFF mode) inwhich none of the HDMI video and audio output function, the recordingfunction, and the main microcomputer function including the IPcommunication function and the LED clock display function is energized,as shown in FIG. 5A.

Note that the same applies to the set-top box 30 and the TV 10, and sotheir description is omitted here.

Though there is also a function such as a remote control receptionfunction that is continuously operational regardless of the operationmode, such a function is not shown in this embodiment. Note that thefunctions shown in each of FIGS. 5A, 5B, and 5C are merely an example ofa part of functions of the corresponding apparatus, and functionsassociated with operation modes are not limited to such.

The user can change the operation mode and function correspondence tableby using the remote control 40 of the TV 10, the DVD recorder 20, andthe set-top box 30.

FIG. 6 shows an example of a menu for setting an operation mode and afunction in the DVD recorder 20 in the first embodiment of the presentinvention. A menu 1600 is an example of an OSD (On Screen Display) menudisplay for changing the operation mode and function correspondence inthe DVD recorder 20. In FIG. 6, menu items 1602 to 1604 each show anoperational function combination when switching to the operation mode,and a cursor 1601 shows a selected menu item.

When the user moves the cursor 1601 and selects a desired menu itemthrough the input unit such as the remote control (not shown) of the DVDrecorder 20, the microcomputer 210 rewrites the operation mode andfunction correspondence table in the operation function setting storageunit 221 so as to have a value corresponding to the selected menu item.

The TV 10 and the set-top box 30 also have the same OSD menu displayfunction. The user can rewrite the operation function setting storageunits 121 and 321 by setting the respective apparatuses so that only adesired function is operational in each operation mode.

(Operation Mode Setting According to Time by the Timer in EachApparatus)

FIG. 7 shows an example of an operation mode switching time settingmethod by an OSD menu display in the TV 10 in the first embodiment ofthe present invention.

First, the user designates the time 1 to start operation in the power-ONoperation mode 1 and the power-OFF operation mode 1 and the time 2 tostart operation in the power-ON operation mode 2 and the power-OFFoperation mode 2, through the input unit of the TV beforehand.

For example, the time 1 and the time 2 are set as follows. In a menusuch as an OSD menu 2100 displayed by the video output unit 106 in theTV 10, the user changes the start times of the operation mode 1 and theoperation mode 2 to desired times by pressing buttons which constitutethe input unit of the TV 10 such as the remote control 40.

After the time 1 and the time 2 are determined by the user operation,the TV 10 transmits, from the CEC communication unit 111, an operationmode switching time setting command having the user-designated time 1and time 2 as a parameter, to the DVD recorder 20 and the set-top box 30connected with the TV 10. The TV also sets the time 1 and the time 2 inthe operation mode switching timer 101.

The DVD recorder 20 and the set-top box 30 receive the operation modeswitching time setting command, and set the time 1 and the time 2designated by the parameter in the received command, respectively in theoperation mode switching timers 201 and 301.

When the time 2 is reached, the operation mode switching timer 201 inthe DVD recorder 20 notifies the microcomputer 210 that the time 2 isreached.

The microcomputer 210 receives the notification. When the operation modeof the DVD recorder 20 is the power-ON operation mode 1, themicrocomputer 210 switches the operation mode to the power-ON operationmode 2. When the operation mode of the DVD recorder 20 is the power-OFFoperation mode 1, the microcomputer 210 switches the operation mode tothe power-OFF operation mode 2. The microcomputer 210 then startsoperation.

Upon switching the operation mode, the DVD recorder 20 references theoperation function setting storage unit 221 in the DVD recorder 20. Fora function that is set to be non-operational in the switched operationmode, the DVD recorder 20 ends a corresponding program or does notenergize the function. For a function that is set to be operational inthe switched operation mode, the DVD recorder 20 starts a correspondingprogram or energizes the function.

For example, in the case where the IP communication unit 218 in the DVDrecorder 20 is set to be non-operational in the power-OFF operation mode2, the DVD recorder 20 ends a program of the IP communication unit 218or does not energize the IP communication unit 218.

Likewise, when the time 2 is reached, the operation mode switching timer301 in the set-top box 30 notifies the microcomputer 310 that the time 2is reached.

The microcomputer 310 receives the notification. When the operation modeof the set-top box 30 is the power-ON operation mode 1, themicrocomputer 310 switches the operation mode to the power-ON operationmode 2. When the operation mode of the set-top box 30 is the power-OFFoperation mode 1, the microcomputer 310 switches the operation mode tothe power-OFF operation mode 2. The microcomputer 310 then startsoperation.

Upon switching the operation mode, the set-top box 30 references theoperation function setting storage unit 321 in the set-top box 30, inthe same manner as the DVD recorder 20. For a function that is set to benon-operational in the switched operation mode, the set-top box 30 endsa corresponding program or does not energize the function. For afunction that is set to be operational in the switched operation mode,the set-top box 30 starts a corresponding program or energizes thefunction.

Likewise, when the time 2 is reached, the operation mode switching timer101 in the TV 10 notifies the microcomputer 110 that the time 2 isreached.

The microcomputer 110 receives the notification. When the operation modeof the TV 10 is the power-ON operation mode 1, the microcomputer 110switches the operation mode to the power-ON operation mode 2. When theoperation mode of the apparatus is the power-OFF operation mode 1, themicrocomputer 110 switches the operation mode to the power-OFF operationmode 2. The microcomputer 110 then starts operation.

The TV 10, the DVD recorder 20, and the set-top box 30 also switch theoperation mode according to the respective operation mode switchingtimers (101, 201, and 301) when the time 1 is reached, in the same wayas above.

When the time 1 is reached, the operation mode switching timer 201 inthe DVD recorder 20 notifies the microcomputer 210 that the time 1 isreached.

The microcomputer 210 receives the notification. When the operation modeof the DVD recorder 20 is the power-ON operation mode 2, themicrocomputer 210 switches the operation mode to the power-ON operationmode 1. When the operation mode of the apparatus is the power-OFFoperation mode 2, the microcomputer 210 switches the operation mode tothe power-OFF operation mode 1. The microcomputer 210 then startsoperation.

Likewise, when the time 1 is reached, the operation mode switching timer301 in the set-top box 30 notifies the microcomputer 310 that the time 1is reached.

The microcomputer 310 receives the notification. When the operation modeof the DVD recorder 20 is the power-ON operation mode 2, themicrocomputer 310 switches the operation mode to the power-ON operationmode 1. When the operation mode of the apparatus is the power-OFFoperation mode 2, the microcomputer 310 switches the operation mode tothe power-OFF operation mode 1. The microcomputer 310 then startsoperation.

Likewise, when the time 1 is reached, the operation mode switching timer101 in the TV 10 notifies the microcomputer 110 that the time 1 isreached.

The microcomputer 110 receives the notification. When the operation modeof the TV 10 is the power-ON operation mode 2, the microcomputer 110switches the operation mode to the power-ON operation mode 1. When theoperation mode of the TV 10 is the power-OFF operation mode 2, themicrocomputer 110 switches the operation mode to the power-OFF operationmode 1. The microcomputer 110 then starts operation.

As described above, when the time to switch the operation mode of theDVD recorder 20 or the set-top box 30 is designated by the user in theTV 10, the DVD recorder 20 or the set-top box 30 sets the designatedtime in the operation mode switching timer 201 or 301 on the basis ofthe control command transmitted from the TV 10. When the designated timeis reached, the DVD recorder 20 or the set-top box 30 switches to theoperation mode designated by the user. Thus, the operation mode isswitched according to the time by the timer in each apparatus.

Note that the operation mode switching time setting is not limited tothe above two times. For instance, the operation mode may be designatedaccording to the day and time, as shown in FIG. 8. Moreover, the numberof operation modes is not limited to two, and three or more operationmodes may be subject to switching.

In addition, the timing of switching the operation mode is not limitedto a time of day, and may instead be an elapsed time. In this case, forexample, when one operation mode continues for a predetermined elapsedtime, the operation mode is switched to another operation mode upon theelapse of the time.

(Operation Mode Switching in Synchronization with Power ON/OFF)

The DVD recorder 20 and the set-top box 30 can also switch to theoperation mode 1 or the operation mode 2 in synchronization with theoperation of the TV 10, without depending on the operation modeswitching timers 201 and 301. The following describes a process wherebythe DVD recorder 20 and the set-top box 30 switch to the operation mode1 or the operation mode 2 in synchronization with the power state of theTV 10, without depending on the operation mode switching timers 201 and301.

The TV power state determination units 216 and 316 in the DVD recorder20 and the set-top box 30 detect a change in power state of the TV 10and determine the power state of the TV 10, respectively via the CECcommunication units 211 and 311.

In order to determine the power state of the TV 10, the TV power statedetermination units 216 and 316 transmit a <Give Power Status> commandto query the power state of the TV 10 at regular time intervals.

The TV 10 receives the <Give Power Status> command, and transmits a<Report Power Status> command having a power-ON state or a power-OFFstate as a parameter, to the apparatus transmitting the <Give PowerStatus> command.

By receiving the <Report Power Status> command at the regular timeintervals, the TV power state determination units 216 and 316 can detecta change in power state of the TV 10 and determine the power state ofthe TV 10.

In the case of transmitting a specific CEC command when the TV 10 ispowered ON or when the TV 10 is powered OFF, the TV power statedetermination units 216 and 316 can determine whether the TV 10 ispowered ON or OFF, upon receiving the specific CEC command.

For example, in the case of transmitting a <Standby> command when the TV10 is powered OFF, the TV power state determination units 216 and 316 inthe DVD recorder 20 and the set-top box 30 can determine that the TV 10is powered OFF, upon receiving the <Standby> command from the TV 10.

The following describes a processing flow when the user powers ON the TV10 by pressing the power button (not shown) on the remote control 40 ofthe TV 10 or a cabinet of the TV 10.

First, the TV power state determination units 216 and 316 in the DVDrecorder 20 and the set-top box 30 detect that the TV 10 is powered ON,and notify the microcomputers 210 and 310 that the TV 10 is powered ON.

Upon detecting the power ON of the TV 10 through the notification, themicrocomputers 210 and 310 in the DVD recorder 20 and the set-top box 30switch the operation mode to the power-ON operation mode 1 or thepower-OFF operation mode 1, and start operation.

When the user powers OFF the TV 10 by pressing the power button (notshown) on the remote control 40 of the TV 10 or the cabinet of the TV 10while the TV 10 is operating in a power-ON state, the TV 10 transmits a<Standby> command for powering OFF a connected apparatus.

The TV power state determination units 216 and 316 in the DVD recorder20 and the set-top box 30 receive the <Standby> command, and determinethat the TV 10 is powered OFF. The TV power state determination units216 and 316 respectively notify the microcomputers 210 and 310 of aresult of the determination.

The microcomputers 210 and 310 in the DVD recorder 20 and the set-topbox 30 detect the power OFF of the TV 10 through the notification. Sincethe <Standby> command has been received, the microcomputers 210 and 310switch the operation mode to the power-OFF operation mode 2 and startoperation.

Thus, the DVD recorder 20 and the set-top box 30 can switch to theoperation mode 1 or the operation mode 2, without depending on theoperation mode switching timers 201 and 301. That is, the DVD recorder20 and the set-top box 30 determine whether the TV 10 is powered ON orOFF, and switch the operation mode in synchronization with the power ONor OFF of the TV 10.

Note that the method whereby the TV power state determination units 216and 316 determine the power state of the TV 10 is not limited to theabove method. As an example, the DVD recorder 20 and the set-top box 30may detect that the TV 10 is powered OFF, by receiving a <Report PowerStatus> command having a power-OFF state of the TV 10 as a parameter.

(Powering OFF the DVD Recorder 20 and the Set-Top Box According to theUser's Viewing Operation)

For example, suppose input selection for video and audio data viewed onthe TV 10 is made from the DVD recorder 20 to the set-top box 30 whilethe DVD recorder 20 is in the operation mode 1 or the operation mode 2.

When the user is viewing video and audio from the set-top box 30 on theTV 10, video and audio data outputted from the DVD recorder 20 cannot beviewed on the TV 10. In such a case, the DVD recorder 20 is powered OFF.The same applies to the set-top box 30. In detail, when the input of theTV 10 is the DVD recorder 20, the set-top box 30 is powered OFF becausevideo and audio data outputted from the set-top box 30 cannot be viewedon the TV 10.

FIG. 9 shows an example of a flow of CEC command transmission andreception when the DVD recorder 20 and the set-top box 30 operateaccording to the user's operation. The following describes a processwhereby the DVD recorder 20 and the set-top box are powered OFFaccording to the user's viewing operation of the TV 10, with referenceto FIG. 9.

First, the user powers ON the TV 10 by operating the input unit of theTV 10 such as the remote control 40 (Step S101).

After the TV 10 is powered ON, in the case of reproducing video andaudio from the tuner 120 included in the TV 10, the TV 10 broadcasts an<Active Source> command to the DVD recorder 20 and the set-top box 30.At this time, both the DVD recorder 20 and the set-top box 30 are not ina power-ON state, so that the DVD recorder and the set-top box 30perform no operation in response to the <Active Source> command (StepsS102, S103).

However, the TV power state determination units 216 and 316 in the DVDrecorder 20 and the set-top box 30 determine that the TV 10 is poweredON by detecting a CEC command transmitted when the TV 10 is powered ON,and notify the microcomputers 210 and 310 that the TV 10 is powered ON.

Upon receiving the notification, the microcomputer 210 references theoperation function setting storage unit 221. When the apparatus is inthe operation mode 1, the microcomputer 210 activates a function that isoperational in a power-ON state of the TV in the power-OFF operationmode 1. When the apparatus is in the operation mode 2, on the otherhand, the microcomputer 210 activates a function that is operational ina power-ON state of the TV 10 in the power-OFF operation mode 2.

Likewise, the microcomputer 310 in the set-top box 30 references theoperation function setting storage unit 321. When the apparatus is inthe operation mode 1, the microcomputer 310 activates a function that isoperational in a power-ON state of the TV 10 in the power-OFF operationmode 1. When the apparatus is in the operation mode 2, on the otherhand, the microcomputer 310 activates a function that is operational ina power-ON state of the TV in the power-OFF operation mode 2.

Next, to start viewing the set-top box 30, the user performs selectionby selecting an OSD menu displayed on the TV 10 or pressing a button onthe remote control 40 of the TV 10 (Step S104).

The TV 10 responsively transmits a power-ON command to the set-top box30 (Step S105).

The set-top box 30 receives the power-ON command, transitions to apower-ON state in the operation mode 1 or the operation mode 2, andstarts outputting video and audio (Step S106). When starting the videoand audio output, the set-top box 30 transmits an <Active Source>command to the TV 10 and the DVD recorder 20, and stores informationthat the set-top box 30 is in an active source state, in the activesource state storage unit 308 in the set-top box 30.

Next, to start viewing the DVD recorder 20, the user performs selectionby selecting a menu displayed on the TV 10 or pressing a button on theremote control 40 of the TV 10 (Step S107).

The TV 10 responsively transmits a power-ON command to the DVD recorder20 (Step S108).

The DVD recorder 20 receives the power-ON command, and references theoperation function setting storage unit 221. The DVD recorder 20transitions to a power-ON state by operating a function corresponding tothe current operation mode. The DVD recorder 20 further startsoutputting video and audio. When starting the video and audio output,the DVD recorder 20 transmits an <Active Source> command to the TV 10and the set-top box 30 (Step S109), and also stores information that theDVD recorder 20 is in an active source state, in the active source statestorage unit 208.

Upon receiving the <Active Source> command transmitted in Step S109, theset-top box 30 determines that another apparatus is in an active sourcestate. The set-top box 30 accordingly deletes the information that theset-top box 30 is in an active source state from the active source statestorage unit 308, and transitions to a power-OFF state (Step S110).

Here, in Step S110, the microcomputer 310 in the set-top box 30references the operation function setting storage unit 321. When theapparatus (the set-top box 30) is in the operation mode 1, themicrocomputer 310 ends an unnecessary function so as to operate only afunction that is operational in a power-ON state of the TV 10 in thepower-OFF operation mode 1. When the apparatus is in the operation mode2, the microcomputer 310 ends an unnecessary function so as to operateonly a function that is operational in a power-ON state of the TV 10 inthe power-OFF operation mode 2.

Likewise, upon receiving an <Active Source> command from an apparatusother than the DVD recorder 20, the DVD recorder determines that anotherapparatus is in an active source state. The DVD recorder 20 accordinglydeletes the information that the DVD recorder 20 is in an active sourcestate from the active source state storage unit 208, and transitions toa power-OFF state (Step S114).

In Step S114, the microcomputer 210 in the DVD recorder 20 referencesthe operation function setting storage unit 221. When the apparatus (theDVD recorder 20) is in the operation mode 1, the microcomputer 210 endsan unnecessary function so as to operate only a function that isoperational in a power-ON state of the TV 10 in the power-OFF operationmode 1. When the apparatus is in the operation mode 2, the microcomputer210 ends an unnecessary function so as to operate only a function thatis operational in a power-ON state of the TV 10 in the power-OFFoperation mode 2.

When the user presses an input selection button of the TV 10, the TV 10transmits a <Set Stream Path> command having, as a parameter, a PA of anapparatus connected to a designated input.

In the case, the DVD recorder 20 or the set-top box 30 is powered ON andtransmits an <Active Source> command, when the PA shown by the parameterin the <Set Stream Path> command is the same as a PA of the apparatus.The DVD recorder 20 or the set-top box 30 then starts outputting videoand audio data, and also stores information that the apparatus is in anactive source state, in the active source state storage unit 208 or 308.

Note that, after the DVD recorder 20 or the set-top box is powered OFFas a result of receiving an <Active Source> command, if no operation isperformed on the apparatus for a predetermined time period through anyof the remote control 40, a button on a cabinet of the set-top box 30,CEC, and the like, it can be assumed that the user's operation on theapparatus does not occur. In such a case, the DVD recorder 20 or theset-top box 30 references the operation function setting storage unit221 or 321, and transitions to a power-OFF state where an unnecessaryfunction is further ended by operating only a function that isoperational in a power-OFF state of the TV 10 in the operation mode 1 orthe operation mode 2. This is described below, with reference to FIG. 9.

Suppose, after Step S114, to view a broadcast by the tuner 120 in the TV10, the user performs selection by selecting an OSD menu displayed onthe TV 10 or pressing a button on the remote control 40 of the TV 10, asshown in FIG. 9 (Step S115).

In this case, the TV 10 transmits an <Active Source> command to the DVDrecorder 20 and the set-top box 30 (Steps S116, S117).

Upon receiving the <Active Source> command transmitted in Step S116, theset-top box 30 determines that another apparatus is in an active sourcestate. The set-top box 30 accordingly deletes the information that theset-top box 30 is in an active source state from the active source statestorage unit 308, and transitions to a power-OFF state (power-OFFoperation mode 1).

Here, the DVD recorder 20 also receives the <Active Source> commandtransmitted in Step S117, but performs no operation in response to thiscommand because the DVD recorder 20 has already transitioned to apower-OFF state (power-OFF operation mode 1) in Step S114.

In the case where, while the user continues viewing the broadcast by thetuner 120 in the TV 10, no operation is performed on the DVD recorder 20and the set-top box 30 for the predetermined time period after the DVDrecorder 20 and the set-top box 30 are powered OFF, the DVD recorder 20and the set-top box 30 switch the operation mode in a power-OFF statefrom the operation mode 1 (power-OFF operation mode 1) to the operationmode 2 (power-OFF operation mode 2).

Here, the DVD recorder 20 and the set-top box 30 in a power-OFF statehave at least two operation modes that differ in electricityconsumption, namely, the power-OFF operation mode 1 and the power-OFFoperation mode 2. As shown in FIG. 5, the power-OFF operation mode 2 hasfewer operational functions than the power-OFF operation mode 1, and sohas lower electricity consumption than the power-OFF operation mode 1.

Therefore, in the DVD recorder 20 and the set-top box 30, the number ofoperational functions when the TV 10 is powered OFF can be reduced ascompared with the number of operational functions when the TV 10 ispowered ON. Moreover, in the case where no operation is performed on theDVD recorder 20 and the set-top box 30 for the predetermined time periodin a power-OFF state, the DVD recorder 20 and the set-top box 30 can beswitched to a power-OFF state of lower electricity consumption, on anassumption that there is no need to immediately power ON the DVDrecorder 20 and the set-top box 30. This further contributes to lowerelectricity consumption, so that a reduction in electricity consumptioncan be achieved.

Note that, in the case where there is no operation even when thepredetermined time period has elapsed as mentioned above, the TV 10which serves as a master apparatus for the DVD recorder 20 and theset-top box 30 may make the assumption that there is no need toimmediately power ON. For example, when there is no operation on the TV10 for the predetermined time period while the user continues viewingthe broadcast by the tuner 120 in the TV 10, the TV 10 transmits acontrol command for controlling another apparatus, to the DVD recorder20 and the set-top box 30. In this case, the DVD recorder 20 and theset-top box 30 switch to a power-OFF state of lower electricityconsumption, on the basis of the received control command.

Moreover, the DVD recorder 20 and the set-top box 30 do not need to beimmediately powered OFF upon receiving the <Active Source> command, andmay instead be powered OFF when no operation is performed for a fixedtime period after the reception.

In the above way, the DVD recorder 20 and the set-top box 30 can each bepowered OFF according to the user's viewing operation. By ending anunnecessary function when the user is not viewing the apparatus, it ispossible to reduce electricity consumption.

(Electricity Consumption Amount Recording)

The TV 10, the DVD recorder 20, and the set-top box 30 each record anamount of electricity consumption, i.e., an amount of electrical powerconsumed in the apparatus, and an amount of saved electricityconsumption achieved as a result of a change in operation state causedby the operation mode switching timer.

In addition, in each of the TV 10, the DVD recorder 20, and the set-topbox 30, a correspondence table of each operation state and electricityconsumption of the apparatus in the operation state is stored in theelectricity consumption storage unit (104, 204, and 304) beforehand.Note that, when there is no significant difference in electricityconsumption between operational function combinations, such combinationsmay be shown together as one state.

The following describes a process whereby the TV 10 obtains an amount ofelectricity consumption and an amount of saved electricity consumption,taking the DVD recorder 20 as an example.

FIG. 10 is a diagram showing an example of a correspondence table ofeach operation state and electricity consumption in the DVD recorder 20.In FIG. 10, electricity consumption is 40 W in an operation state E1, 10W in an operation state E2, and 0.5 W in an operation state E3 in theDVD recorder 20.

When the DVD recorder 20 changes in operation state as a result of theuser's operation of the input unit (not shown), the CEC commandreception, or the operation of the timer in the DVD recorder such as therecording timer 217 or the operation mode switching timer 201, the DVDrecorder 20 stores a start time of the operation state and informationshowing the operation state in the operation state storage unit 222.

In the case where the change of the operation state is caused by theoperation mode switching timer 201, the DVD recorder also stores a flagshowing that the state change is caused by the operation mode switchingtimer 201, in the operation state storage unit 222.

After this, when the DVD recorder 20 changes in operation state, the DVDrecorder 20 calculates an amount of electricity consumption and anamount of saved electricity consumption in the operation state beforethe change. This is described in detail below.

First, the DVD recorder 20 references the operation state storage unit222, and calculates a difference between the start time of the operationstate and the current time as a duration of the operation state.

Next, the DVD recorder 20 references the operation state before thechange in the operation state storage unit 222, and obtains electricityconsumption in the operation state with reference to the electricityconsumption storage unit 204.

The DVD recorder 20 then calculates a product of the duration of theoperation state and the electricity consumption in the operation state,as the amount of electricity consumption in the operation state. The DVDrecorder 20 stores the amount of electricity consumption, by adding theamount of electricity consumption to a value stored in the current-daystorage unit in the electricity consumption amount storage unit 202. TheDVD recorder also stores the current time and the operation state afterthe change, in the operation state storage unit 222.

In the same manner, when the DVD recorder 20 changes in operation stateagain, an amount of electricity consumption is calculated from a productof a duration of the operation state and electricity consumption, andthe amount of electricity consumption is stored by being added to thevalue stored in the current-day storage unit in the electricityconsumption amount storage unit 202. The above series of operations isrepeated in this way.

Moreover, the DVD recorder 20 references the operation state storageunit 222 and, when the state change is caused by the operation modeswitching timer 201, calculates the amount of saved electricityconsumption. The amount of saved electricity consumption is calculatedby the following procedure.

The DVD recorder 20 calculates a difference between the electricityconsumption in the operation state stored in the operation state storageunit 222 and electricity consumption in a normal state. The DVD recorder20 then calculates a product of the electricity consumption differenceand the duration of the operation state, as the amount of savedelectricity consumption.

Here, the electricity consumption in the normal state is electricityconsumption in an operation state in the case of not setting theoperation mode switching timer 201. Accordingly, the amount of savedelectricity consumption indicates an amount of electricity consumptionreduced by the operation of the operation mode switching timer 201. Theamount of saved electricity consumption is stored by being added to avalue in the current-day storage unit in the saved electricityconsumption amount storage unit 203, in the same way as the amount ofelectricity consumption.

Furthermore, the electricity consumption amount storage unit 202 storesa pair of a value corresponding to the current day and a recording dateand time in the log recording unit in the electricity consumption amountstorage unit 202, at regular time intervals such as 24-hour intervals.The electricity consumption amount storage unit 202 also resets thevalue in the current-day storage unit in the electricity consumptionamount storage unit 202 to 0.

Likewise, the saved electricity consumption amount storage unit 203stores a pair of a value corresponding to the current day and arecording date and time in the log recording unit in the savedelectricity consumption amount storage unit 203, at regular timeintervals such as 24-hour intervals. The saved electricity consumptionamount storage unit 203 also resets the value in the current-day storageunit in the saved electricity consumption amount storage unit 203 to 0.

Note that the time intervals of recording a log of the amount ofelectricity consumption and the amount of saved electricity consumptionare not limited to 24-hour intervals, so long as they are regular timeintervals.

Each log recording unit records, for example, a log corresponding to 30days, and deletes the log in order of occurrence when 30 days areexceeded.

In addition to the above-mentioned operations, the DVD recorder 20stores, together with the current time, information that there is nochange in operation state of the DVD recorder 20, in the operationduration time storage unit in the operation state storage unit 222 atpredetermined time intervals.

There is the case where power supply to the DVD recorder 20 is stoppedby, for example, the user removing a power cable of the DVD recorder 20from a receptacle. When this occurs, upon receiving power supply again,the DVD recorder 20 starts operation, and also obtains the operationstate, the start time of the operation state, and the duration time ofthe operation state with reference to the operation state storage unit222. The DVD recorder calculates a difference between the start time ofthe operation state and the duration time of the operation state, andstores a product of the difference and the electricity consumption inthe operation state by adding the product to the value in thecurrent-day storage unit in the electricity consumption amount storageunit 202.

FIG. 11 shows an example of changes in operation and electricityconsumption of the DVD recorder 20. The following describes an exampleof storing the amount of electricity consumption and the amount of savedelectricity consumption, with reference to FIG. 1. In FIG. 11, ahorizontal axis represents a time, and a vertical axis representselectricity consumption at the time.

First, when the DVD recorder 20 is connected to the receptacle (notshown) and starts operation in the operation state E3 at 0 o'clock,information that the operation state E3 starts at 0 o'clock is stored inthe operation state storage unit 222.

Following this, the user powers ON the DVD recorder 20 at 1 o'clock(“power ON A” in FIG. 11). Since a duration of the operation state E3 is1 hour from 0 o'clock to 1 o'clock, 0.5 W (the electricity consumptionof the operation state E3)×1 hour=0.5 Wh is stored in the current-daystorage unit in the electricity consumption amount storage unit 202.Meanwhile, as a result of changing to the operation state E1,information that the operation state E1 starts at 1 o'clock is stored inthe operation state storage unit 222.

Next, the user powers OFF the DVD recorder 20 at 2 o'clock (“power OFF”in FIG. 11). Since a duration of the operation state E1 is 1 hour from 1o'clock to 2 o'clock, 40 W (the electricity consumption of the operationstate E1)×1 hour=40 Wh is stored in the current-day storage unit in theelectricity consumption amount storage unit 202. This yields 40.5 Wh asthe amount of electricity consumption of the current day. Meanwhile,information that the operation state E2 starts at 2 o'clock is stored inthe operation state storage unit 222.

Next, the operation mode switching timer 201 operates to change to theoperation state E3 at 3 o'clock (“operation state switching timer” inFIG. 11). Since a duration of the operation state E2 is 1 hour from 2o'clock to 3 o'clock, 10 W (the electricity consumption of the operationstate E2)×1 hour=10 Wh is stored in the current-day storage unit in theelectricity consumption amount storage unit 202. This yields 50.5 Wh asthe amount of electricity consumption of the current day. Meanwhile,information that the operation state E3 starts at 3 o'clock and thechange of the operation state is caused by the operation mode switchingtimer 201 is stored in the operation state storage unit 222.

After this, the user powers ON the DVD recorder 20 at 6 o'clock, as aresult of which the operation state changes to the operation state E1.Since a duration of the operation state E3 is from 3 o'clock to 6o'clock, 0.5 W (the electricity consumption of the operation state E3)×3hours=1.5 Wh is stored in the current-day storage unit in theelectricity consumption amount storage unit 202. This yields 52 Wh asthe amount of electricity consumption of the current day.

Moreover, since the change to the operation state E3 is caused by theoperation mode switching timer 201, the amount of saved electricityconsumption is calculated. The DVD recorder 20 is changed to theoperation state E3 by the operation mode switching timer 201, instead ofthe operation state E2 which is a normal operation state when the userpowers OFF the DVD recorder 20. Accordingly, 9.5 W (the differencebetween the electricity consumption of the operation state E2 and theelectricity consumption of the operation state E3)×3 hours=28.5 Wh isstored in the current-day storage unit in the saved electricityconsumption amount storage unit 203. Meanwhile, information that theoperation state E1 starts at 6 o'clock is stored in the operation statestorage unit 222.

Thus, the DVD recorder 20 can calculate the amount of electricityconsumption and the amount of saved electricity consumption.

In the same manner, the TV 10 and the set-top box 30 can obtain theamount of electricity consumption and the amount of saved electricityconsumption, respectively using the operation state storage units 122and 322, the electricity consumption storage units 104 and 304, theelectricity consumption amount storage units 102 and 302, and the savedelectricity consumption amount storage units 103 and 303.

(Electricity Consumption Amount Display by the TV 10)

The following describes the case where the user operates the remotecontrol 40 of the TV 10 or a menu of the TV 10 to display an amount ofelectricity consumption and an amount of saved electricity consumption.

First, the TV 10 transmits an electricity consumption amount requestcommand requesting electricity consumption amount information and asaved electricity consumption amount request command requesting savedelectricity consumption amount information, to a connected apparatus.

The DVD recorder 20 and the set-top box 30 receive the electricityconsumption amount request command. The DVD recorder 20 and the set-topbox 30 respectively reference information in the log recording units inthe electricity consumption amount storage units 202 and 302, andtransmit an electricity consumption amount notification command having,as a parameter, a pair of an amount of electricity consumption and arecording date and time, to the TV 10.

The DVD recorder 20 and the set-top box 30 also receive the savedelectricity consumption amount request command. The DVD recorder 20 andthe set-top box 30 respectively reference information in the logrecording units in the saved electricity consumption amount storageunits 203 and 303, and transmit a saved electricity consumption amountnotification command having, as a parameter, a pair of an amount ofsaved electricity consumption and a recording date and time, to the TV10.

Having received the electricity consumption amount notification commandfrom each of the DVD recorder 20 and the set-top box 30, the TV 10calculates a total amount of electricity consumption of the apparatuses,and displays the amount of electricity consumption on a daily basis.

FIG. 12 shows an example of displaying, on the TV 10, an operation stateof each apparatus and a total amount of electricity consumption of theAV system in the first embodiment of the present invention.

For example, as shown by an OSD display 2002 in FIG. 12, an amount ofelectricity consumption from 30 days ago up to 1 day ago can bedisplayed where a horizontal axis represents a time and a vertical axisrepresents an amount of electricity consumption.

Likewise, having received the saved electricity consumption amountnotification command from each of the DVD recorder 20 and the set-topbox 30, the TV 10 calculates a total amount of saved electricityconsumption on a daily basis and displays it in the video output unit106. Here, values stored in the electricity consumption amount storageunit 102 and the saved electricity consumption amount storage unit 103in the TV 10 may be added respectively to the displayed amount ofelectricity consumption and amount of saved electricity consumption.

Note that the display of each of the amount of electricity consumptionand the amount of saved electricity consumption may be performed bydisplaying the number of icons proportional to the amount.

Moreover, the amount of electricity consumption and the amount of savedelectricity consumption may be OSD-displayed when the user powers ON theTV 10 and the TV 10 starts video output.

Thus, the amount of electricity consumption and the amount of savedelectricity consumption of the TV 10, the DVD recorder 20, and theset-top box 30 can be displayed to the user.

As described above, according to the first embodiment, a masterapparatus (the TV 10 in this embodiment) transmits a control command forcontrolling an apparatus other than the master apparatus to the otherapparatus, thereby enabling the other apparatus to switch its operationstate on the basis of the received control command. This contributes tohigher electricity consumption efficiency in the AV system.

Therefore, in the AV system where a plurality of apparatuses that eachhave a plurality of operation states of different electricityconsumption are connected via a communication network such as HDMI, theplurality of operation states in the plurality of apparatuses can becontrolled so as to improve electricity consumption efficiency in the AVsystem.

Second Embodiment

A second embodiment has the same structures and functions as the firstembodiment described above, and so the same structures as the firstembodiment are given the same reference numerals in the drawings andtheir description is omitted.

<Structure>

FIG. 13 is a diagram schematically showing a structure of an AV systemin the second embodiment. FIG. 14 is a functional block diagram of a TV50 in the second embodiment. FIG. 15 is a functional block diagram of aDVD recorder 60 in the second embodiment. FIG. 16 is a functional blockdiagram of a set-top box 70 in the second embodiment. Note that, inFIGS. 14, 15, and 16, the same components as those in FIGS. 2, 3, and 4are given the same reference numerals and their detailed description isomitted here.

The TV 50 in the second embodiment is an example of the first apparatusaccording to the present invention, and the DVD recorder 60 and theset-top box 70 in the second embodiment are each an example of thesecond apparatus according to the present invention.

As shown in FIG. 13, the AV system in the second embodiment includes theTV 50, the DVD recorder 60, and the set-top box 70. The AV system alsoincludes, for example, the remote control 40.

In the AV system, the DVD recorder 60 and the set-top box 70 areconnected to the TV 50 via HDMI cables. CEC lines in in HDMI areconnected in a CEC communication unit 511 in the TV 50. The TV 50, theDVD recorder 60, and the set-top box 70 are capable of performingtransmission and reception of a CEC command as a control command witheach other.

The TV 50 is an apparatus that outputs video and audio outputted from anapparatus connected via a HDMI cable, and a broadcast signal receivedvia an antenna (not shown).

The TV 50 includes an operation mode switching timer 501, an electricityconsumption amount storage unit 502, a saved electricity consumptionamount storage unit 503, the electricity consumption storage unit 104,the remote control reception unit 105, the video output unit 106, theaudio output unit 107, the active source apparatus storage unit 108, theconnected apparatus list storage unit 109, a microcomputer 510, the CECcommunication unit 511, the TMDS decoding unit 112, the TMDS input unit113, the HDMI input units 114 and 115, the tuner 120, and the operationfunction setting storage unit 121.

The operation mode switching timer 501 includes a timer and an operationmode switching time storage unit.

The operation mode switching timer 501 stores the time 1 to switch tothe operation mode 1 and the time 2 to switch to the operation mode 2,via the microcomputer 510. When the time 1 or the time 2 is reached, theoperation mode switching timer 501 notifies the microcomputer 510 thatthe corresponding set time is reached.

The electricity consumption amount storage unit 502 includes acurrent-day storage unit that temporarily stores an amount ofelectricity consumption of a current day, and a log recording unit thatstores an amount of electricity consumption of a past fixed time period.In the electricity consumption amount storage unit 502, the current-daystorage unit and the log recording unit are connected via CEC, andperform recording for each apparatus that differs in LA and PA. Notethat the log recording unit in the electricity consumption amountstorage unit 502 is composed of a nonvolatile storage device.

The saved electricity consumption amount storage unit 503 includes acurrent-day storage unit that temporarily stores an amount of savedelectricity consumption of the current day, and a log recording unitthat stores an amount of saved electricity consumption of the past fixedtime period. In the saved electricity consumption amount storage unit503, the current-day storage unit and the log recording unit areconnected by CEC, and perform recording for each apparatus that differsin LA and PA. Note that the log recording unit in the saved electricityconsumption amount storage unit 503 is composed of a nonvolatile storagedevice.

The DVD recorder 60 is an apparatus that records a broadcast signalreceived via an antenna (not shown), and outputs a recorded video andaudio signal via a HDMI cable. As shown in FIG. 15, the DVD recorder 60includes the electricity consumption storage unit 204, the remotecontrol reception unit 205, a microcomputer 610, a CEC communicationunit 611, the decoding unit 212, the TMDS output unit 213, the HDMIoutput unit 214, the recording timer 217, the IP communication unit 218,the recording unit 219, the tuner 220, and the operation functionsetting storage unit 221.

The set-top box 70 is an apparatus that decodes a broadcast signalreceived via a broadcast signal cable (not shown), and outputs a videoand audio signal via a HDMI cable. As shown in FIG. 16, the set-top box70 includes the electricity consumption storage unit 304, the remotecontrol reception unit 305, a microcomputer 710, a CEC communicationunit 711, the decoding unit 312, the TMDS output unit 313, the HDMIoutput unit 314, the tuner 320, and the operation function settingstorage unit 321.

<Operation>

Operations of the TV 50, the DVD recorder 60, and the set-top box 70 inthe second embodiment are described in detail below.

(Operation Mode Switching According to Time)

First, the user designates the time 1 to start operation in the power-ONoperation mode 1 and the power-OFF operation mode 1 and the time 2 tostart operation in the power-ON operation mode 2 and the power-OFFoperation mode 2, through the input unit of the TV 50 beforehand. The TV50 stores the time 1 and time 2.

When the time 2 designated by the user beforehand is reached, theoperation mode switching timer 501 in the TV 50 notifies themicrocomputer 510 that the time 2 is reached.

The microcomputer 510 receives the notification, and controls the CECcommunication unit 511 to transmit an operation mode switching command 2instructing to switch from the operation mode 1 to the operation mode 2.

The DVD recorder 60 and the set-top box 70 each receive the operationmode switching command and, when the operation mode of the apparatus isthe power-ON operation mode 1, switch the operation mode to the power-ONoperation mode 2. When the operation mode of the apparatus is thepower-OFF operation mode 1, on the other hand, the DVD recorder 60 andthe set-top box 70 each switch the operation mode to the power-OFFoperation mode 2.

Upon switching the operation mode, the DVD recorder 60 references theoperation function setting storage unit 221 in the DVD recorder 60. Fora function that is set to be non-operational in the switched operationmode, the DVD recorder 60 ends a corresponding program or does notenergize the function. For a function that is set to be operational inthe switched operation mode, the DVD recorder 60 starts a correspondingprogram or energizes the function.

Upon switching the operation mode, the set-top box 70 references theoperation function setting storage unit 321 in the set-top box 70, inthe same manner as the DVD recorder 60. For a function that is set to benon-operational in the switched operation mode, the set-top box 70 endsa corresponding program or does not energize the function. For afunction that is set to be operational in the switched operation mode,the set-top box 70 starts a corresponding program or energizes thefunction.

Moreover, when the operation mode of the TV 50 is the power-ON operationmode 1, the TV 50 switches the operation mode to the power-ON operationmode 2. When the operation mode of the TV 50 is the power-OFF operationmode 1, on the other hand, the TV 50 switches the operation mode to thepower-OFF operation mode 2. The TV 50 then starts operation.

Subsequently, when the time 1 designated by the user beforehand isreached, the operation mode switching timer 501 in the TV 50 notifiesthe microcomputer 510 that the time 1 is reached. The microcomputer 510receives the notification, and controls the CEC communication unit 511to transmit an operation mode switching command 1 instructing to switchfrom the operation mode 2 to the operation mode 1.

The DVD recorder 60 and the set-top box 70 each receive the operationmode switching command and, when the operation mode of the apparatus isthe power-ON operation mode 2, switch the operation mode to the power-ONoperation mode 1. When the operation mode of the apparatus is thepower-OFF operation mode 2, on the other hand, the DVD recorder 60 andthe set-top box 70 each switch the operation mode to the power-OFFoperation mode 1.

Upon switching the operation mode, the DVD recorder 60 references theoperation function setting storage unit 221 in the DVD recorder 60. Fora function that is set to be non-operational in the switched operationmode, the DVD recorder 60 ends a corresponding program or does notenergize the function. For a function that is set to be operational inthe switched operation mode, the DVD recorder 60 starts a correspondingprogram or energizes the function.

Upon switching the operation mode, the set-top box 70 references theoperation function setting storage unit 321 in the set-top box 70, inthe same manner as the DVD recorder 60. For a function that is set to benon-operational in the switched operation mode, the set-top box 70 endsa corresponding program or does not energize the function. For afunction that is set to be operational in the switched operation mode,the set-top box 70 starts a corresponding program or energizes thefunction.

Moreover, when the operation mode of the TV 50 is the power-ON operationmode 2, the TV 50 switches the operation mode to the power-ON operationmode 1. When the operation mode of the TV 50 is the power-OFF operationmode 2, on the other hand, the TV 50 switches the operation mode to thepower-OFF operation mode 1.

Note that, when the TV 50 is in a power-ON state, the TV 50 does notneed to transmit the operation mode switching command. However, in thecase where the TV 50 is powered OFF in a period during which the TV 50is set to operate in the operation mode 2, that is, a period from thetime 2 to the next time 1, the TV 50 transmits a <Standby> command forpowering OFF and also transmits the operation mode switching command 2.

Moreover, when a function of a high priority is operating in the DVDrecorder 60 or the set-top box 70 as in the case where, for example, aTV program is being recorded, the DVD recorder 60 or the set-top box 70buffers the operation mode switching command in the CEC communicationunit 611 or 711 and, upon completion of the operation of the function,executes the operation mode switching command.

Thus, the TV 50, the DVD recorder 60, and the set-top box 70 can switchthe operation mode according to the time or time period designated bythe user beforehand, through the use of the operation mode switchingtimer 501.

(Operation Mode Switching in Synchronization with Power ON/OFF)

The TV 50, the DVD recorder 60, and the set-top box 70 can also switchto the operation mode 1 or the operation mode 2 in synchronization withthe user's operation on the TV 50, without depending on the operationmode switching timer 501 mentioned above. This is described below.

Suppose the user presses an operation mode switching button (not shown)on the remote control 40 of the TV 50 or the cabinet of the TV 50, whenthe TV 50 is operating in the operation mode 2. In this case, themicrocomputer 510 in the TV 50 controls the CEC communication unit 511to transmit an operation mode switching command 3 instructing to switchto the operation mode 1, to the DVD recorder 60 and the set-top box 70.

The DVD recorder 60 and the set-top box 70 receive the operation modeswitching command 3, switch their operation mode to the power-ONoperation mode 1 or the power-OFF operation mode 1, and start operation.

Suppose the user presses the operation mode switching button (not shown)on the remote control 40 of the TV 50 or the cabinet of the TV 50, whenthe TV 50 is operating in the operation mode 1. In this case, themicrocomputer 510 in the TV 50 controls the CEC communication unit 511to transmit an operation mode switching command 4 instructing to switchto the operation mode 2, to the DVD recorder 60 and the set-top box 70connected with the TV 50.

Note that, when the TV 50 switches from the operation mode 1 to theoperation mode 2, the TV 50 may be powered OFF and transmit, togetherwith the operation mode switching command 4, a <Standby> command forpowering OFF an apparatus connected via CEC.

The DVD recorder 60 and the set-top box 70 receive the operation modeswitching command 4, switch their operation mode to the power-ONoperation mode 2 or the power-OFF operation mode 2, and start operation.

In the case where the TV 50 transmits the <Standby> command togetherwith the operation mode switching command 4, the DVD recorder 60 and theset-top box 70 are powered OFF and switch to the power-OFF operationmode 2.

Thus, the TV 50, the DVD recorder 60, and the set-top box 70 can switchto the operation mode 1 or the operation mode 2 without depending on theoperation mode switching timer 501.

Note that the operation performed by the user so that the TV 50transmits the operation mode switching command 3 or the operation modeswitching command 4 to switch the operation mode is not limited to theoperation mode switching button on the remote control 40 of the TV 50.For example, a menu item for switching the operation mode may beprovided in a menu of the TV 50 so that the operation mode is switchedwhen the user selects the menu item.

Moreover, the TV 50 may be powered OFF and transmit the operation modeswitching command when a predetermined time period has elapsed withoutthe user's operation. Furthermore, the TV 50 may learn a tendency as toduring which time of day the user operates the TV 50, and shorten thetime period to the power OFF in a time of day during which the user doesnot tend to operate the TV 50. This allows for more electrical powersaving.

(Operation Mode Switching According to User Operation)

The TV 50, the DVD recorder 60, and the set-top box 70 can also switchthe operation mode in synchronization with the user's operation on theTV 50, without depending on the operation mode switching timer 501.Besides, even when the operation mode switching timer 501 has been set,it is possible to switch to the operation mode 3 only in accordance withthe user's operation, without performing operation mode switching by thetimer.

The following describes switching from the operation mode 1 or theoperation mode 2 to the operation mode 3, and switching from theoperation mode 3 to the operation mode 1 or the operation mode 2.

Suppose the user presses the operation mode switching button (not shown)on the remote control 40 of the TV 50 or the cabinet of the TV 50, whenthe TV 50 is operating in the operation mode 1 or the operation mode 2.In this case, the microcomputer 510 in the TV 50 controls the CECcommunication unit 511 to transmit an operation mode switching command 5instructing to switch to the operation mode 3, to the DVD recorder 60and the set-top box 70 connected with the TV 50.

Note that, when the TV 50 switches from the operation mode 1 or theoperation mode 2 to the operation mode 3, the TV 50 may be powered OFFand transmit, together with the operation mode switching command 5, a<Standby> command for powering OFF an apparatus connected via CEC.

The DVD recorder 60 and the set-top box 70 receive the operation modeswitching command 5, and switch their operation mode to the power-OFFoperation mode 3.

In the case where the TV 50 transmits the <Standby> command togetherwith the operation mode switching command 5, the DVD recorder 60 and theset-top box 70 are powered OFF and switch to the operation mode 3.

Suppose the user presses the operation mode switching button (not shown)on the remote control 40 of the TV 50 or the cabinet of the TV 50, whenthe TV 50 is operating in the operation mode 3. In this case, themicrocomputer 510 in the TV 50 controls the CEC communication unit 511to transmit an operation mode switching command 6 instructing to clearthe operation mode 3, to the DVD recorder 60 and the set-top box 70connected with the TV 50.

Here, the TV 50 adds a parameter to the operation mode switching command6 so as to switch to the operation mode 1 or the operation mode 2 afterclearing the operation mode 3, and transmits the operation modeswitching command 6. For example, in the case of transmitting theoperation mode switching command 6 in a period from the time 1 to thetime 2, the TV 50 adds the parameter so as to switch to the operationmode 1. In the case of transmitting the operation mode switching command6 in a period from the time 2 to the next time 1, the TV 50 adds theparameter so as to switch to the operation mode 2.

The DVD recorder 60 and the set-top box 70 receive the operation modeswitching command 6, switch their operation mode to the power-ONoperation mode 1 or 2 or the power-OFF operation mode 1 or 2, and startoperation.

Thus, the TV 50, the DVD recorder 60, and the set-top box 70 can switchfrom the operation mode 1 or the operation mode 2 to the operation mode3 on the basis of the received control command, without depending on theoperation mode switching timer 501.

Note that the operation performed by the user so that the TV 50transmits the operation mode switching command 5 or the operation modeswitching command 6 to switch the operation mode is not limited to thepress of the operation mode switching button on the remote control 40 ofthe TV 50. For example, the operation mode may be switched when the userpresses the power button on the remote control 40. Alternatively, a menuitem for switching the operation mode may be provided in a menu of theTV 50 so that the operation mode is switched when the user selects themenu item. Moreover, the switching to the operation mode 3 may beperformed when there is no user operation within a predetermined timeperiod, such as 24 hours, after the user powers OFF the TV 50.Furthermore, the TV 50 may learn a tendency as to during which time ofday the user operates the TV 50, and shorten the time period to switchto the operation mode 3 in a time of day during which the user does nottend to operate the TV 50.

FIG. 17 shows an example of an OSD menu for setting a function that isoperational in the operation mode 3 and switching to the operation mode3 in the TV 50 according to the present invention.

For instance, the TV 50 displays a menu such as an OSD menu 3100 shownin FIG. 17. When the user selects a desired menu item, the CECcommunication unit 511 in the TV 50 transmits an operation functionsetting update command that includes information for setting a functioncombination corresponding to the menu item to be operational in theoperation mode 3, to the DVD recorder 60 and the set-top box 70. The CECcommunication unit 511 also transmits the operation mode switchingcommand 5 instructing to switch to the operation mode 3, to the DVDrecorder 60 and the set-top box 70. Upon receiving the operationfunction setting update command, the DVD recorder 60 and the set-top box70 update the operation function setting storage units 221 and 321 sothat the function combination shown by the operation function settingupdate command is set as a function operational in the operation mode 3.

The DVD recorder 60 and the set-top box 70 also receive the operationmode switching command 5, switch to the operation mode 3, and startoperation in the operation mode 3.

Thus, the TV 50, the DVD recorder 60, and the set-top box 70 can switchthe operation mode in accordance with the user's operation.

(Operations of the DVD Recorder 60 and the Set-Top Box 70 When the TV 50is in a Power-ON State)

When video and audio data outputted from the DVD recorder 60 cannot bereproduced in the TV 50 as in the case where the user is viewing videoand audio from the set-top box 70 in the TV 50 in the operation mode 1or the operation mode 2, the DVD recorder 60 is powered OFF.

Likewise, when video and audio data outputted from the set-top box 70cannot be reproduced in the TV 50 as in the case where the input of theTV 50 is the DVD recorder 60, the set-top box 70 is powered OFF.

FIG. 18 shows an example of a flow of CEC command transmission andreception when the DVD recorder 60 and the set-top box 70 operateaccording to the user's operation in the second embodiment of thepresent invention. The following describes a process whereby the DVDrecorder 60 and the set-top box 70 are powered OFF according to theuser's viewing operation of the TV 50, with reference to FIG. 18.

First, the user powers ON the TV 50 by performing an input operationthrough the input unit of the TV 50 such as the remote control 40 (StepS201).

After the TV 50 is powered ON, in the case of reproducing video andaudio from the tuner 120 included in the TV 50, the TV 50 broadcasts an<Active Source> command to the DVD recorder 60 and the set-top box 70.

The TV 50 also transmits an activation notification command from the CECcommunication unit 511 to the DVD recorder 60 and the set-top box 70.

The microcomputers 610 and 710 in the DVD recorder 60 and the set-topbox 70 receive the activation notification command from the CECcommunication units 611 and 711, and reference the operation functionsetting storage units 221 and 321, respectively. In each of the DVDrecorder 60 and the set-top box 70, when the apparatus is in theoperation mode 1, the microcomputer activates a function that isoperational in a power-ON state of the TV 50 in the power-OFF operationmode 1. When the apparatus is in the operation mode 2, on the otherhand, the microcomputer activates a function that is operational in apower-ON state of the TV 50 in the power-OFF operation mode 2.

Next, to start viewing the set-top box 70, the user performs selectionby selecting a menu displayed on the TV 50 or pressing a button on theremote control 40 of the TV 50 (Step S204).

The TV 50 responsively transmits a power-ON command to the set-top box70 (Step S205).

The set-top box 70 receives the power-ON command, transitions to apower-ON state, and starts outputting video and audio. When starting thevideo and audio output, the set-top box 70 transmits an <Active Source>command to the TV 50 and the DVD recorder 60.

Upon receiving the <Active Source> command, the TV 50 stores a LA and aPA of the transmitter of the command, in the active source apparatusstorage unit 108 in the TV 50.

Next, to start viewing the DVD recorder 60, the user performs selectionby selecting a menu displayed on the TV 50 or pressing a button on theremote control 40 of the TV 50 (Step S207).

The TV 50 responsively transmits a power-ON command to the DVD recorder60 (Step S208).

The DVD recorder 60 receives the power-ON command, transitions to apower-ON state, and starts outputting video and audio. When starting thevideo and audio output, the DVD recorder 60 transmits an <Active Source>command to the TV 50 and the set-top box 70.

Upon receiving the <Active Source> command, the TV 50 references theactive source apparatus storage unit 108 in the TV 50. When a PA of thetransmitter of the received command does not match the PA in the activesource apparatus storage unit 108, the TV 50 determines that the activesource is changed. The TV 50 transmits a power-OFF command to the LA inthe active source apparatus storage unit 108, that is, the set-top box70 in this embodiment (Step S209).

The TV 50 also stores a LA and the PA of the transmitter of the <ActiveSource> command, in the active source apparatus storage unit 108.

The set-top box 70 receives the power-OFF command, and transitions to apower-OFF state. Here, in Step S209, the microcomputer 710 in theset-top box 70 references the operation function setting storage unit321.

When the set-top box 70 is in the operation mode 1, the microcomputer710 ends an unnecessary function so as to operate only a function thatis operational in a power-ON state of the TV 50 in the power-OFFoperation mode 1. When the set-top box 70 is in the operation mode 2,the microcomputer 710 ends an unnecessary function so as to operate onlya function that is operational in a power-ON state of the TV 50 in thepower-OFF operation mode 2.

Next, the user operates the remote control 40 of the set-top box 70 tostart video and audio output. The set-top box 70 transmits an <ActiveSource> command from the CEC communication unit 711 to the TV 50 and theDVD recorder 60 (Step S213).

Upon receiving the <Active Source> command from the set-top box 70, theTV 50 references the active source apparatus storage unit 108. When theactive source is changed, the TV 50 transmits a power-OFF command to theLA in the active source apparatus storage unit 108, that is, the DVDrecorder 60 (Step S214).

The DVD recorder 60 receives the power-OFF command, and transitions to apower-OFF state.

Here, the microcomputer 610 in the DVD recorder 60 references theoperation function setting storage unit 221. When the DVD recorder 60 isin the operation mode 1, the microcomputer 610 ends an unnecessaryfunction so as to operate only a function that is operational in apower-ON state of the TV 50 in the power-OFF operation mode 1. When theDVD recorder 60 is in the operation mode 2, the microcomputer 610 endsan unnecessary function so as to operate only a function that isoperational in a power-ON state of the TV 50 in the power-OFF operationmode 2.

Note that, when transmitting the power-OFF command, the TV 50 may notifythe user that the connected apparatus is powered OFF. For example, whenthe user switches to the set-top box 70 while viewing the DVD recorder60, the TV 50 transmits the power-OFF command to the DVD recorder 60,and also notifies the user that the DVD recorder 60 is powered OFF,through a display such as an OSD display 3201 shown in FIG. 19 in thevideo output device.

When the user presses an input selection button of the TV 50, the TV 50transmits a <Set Stream Path> command having, as a parameter, a PA of anapparatus connected to a designated input.

In this case, the DVD recorder 60 or the set-top box 70 is powered ONand transmits an <Active Source> command, when the PA shown by theparameter in the <Set Stream Path> command is the same as the PA of theapparatus. The DVD recorder 60 or the set-top box 70 then startsoutputting video and audio data.

Note that, when a function of a high priority is operating as in thecase where, for example, a TV program is being recorded, the DVDrecorder 60 or the set-top box 70 buffers the power-OFF command in theCEC communication unit 611 or 711 and, upon completion of the operationof the function, executes the power-OFF command.

In the above way, the DVD recorder 60 and the set-top box 70 can each bepowered OFF according to the user's viewing operation on the TV 50. Byending an unnecessary function when the user is not viewing theapparatus, it is possible to reduce electricity consumption.

(Electricity Consumption Amount Recording)

The TV 50, the DVD recorder 60, and the set-top box 70 each record anamount of electricity consumption, i.e., an amount of electrical powerconsumed in the apparatus, and an amount of saved electricityconsumption achieved as a result of a change in operation state causedby the operation mode switching timer.

In addition, in each of the TV 50, the DVD recorder 60, and the set-topbox 70, a correspondence table of each operation state and electricityconsumption of the apparatus in the operation state is stored in theelectricity consumption storage unit (104, 204, and 304) beforehand.Note that, when there is no significant difference in electricityconsumption between operational function combinations, such combinationsmay be shown together as one state.

The following describes a process whereby the TV 50 obtains an amount ofelectricity consumption and an amount of saved electricity consumptionin the DVD recorder 60. Note that the correspondence of each operationstate and electricity consumption in the DVD recorder 60 is the same asthat in the DVD recorder 20 in the first embodiment.

First, the TV 50 transmits an operation state electricity consumptionrequest command to the DVD recorder 60, at regular time intervals suchas 1-hour intervals.

Upon receiving the operation state electricity consumption requestcommand, the DVD recorder 60 references the electricity consumptionstorage unit 204 to obtain electricity consumption in a currentoperation state. The DVD recorder 60 transmits an operation stateelectricity consumption notification command having, as a parameter,information showing the current operation state and the currentelectricity consumption, to the TV 50.

The TV 50 receives the operation state electricity consumptionnotification command, and calculates a product of the electricityconsumption of the DVD recorder 60 shown by the parameter in theoperation state electricity consumption notification command and thetransmission time interval of the operation state electricityconsumption request command. The TV 50 adds the product to a valuestored in the electricity consumption amount storage unit 502. In thisway, the amount of electricity consumption of the DVD recorder 60 isstored in the electricity consumption amount storage unit 502.

Moreover, the TV 50 transmits an operation state saved electricityrequest command to the DVD recorder 60, at regular time intervals suchas 1-hour intervals.

The DVD recorder 60 receives the operation state saved electricityrequest command. When the current operation state is caused by theabove-mentioned operation mode switching, the DVD recorder 60 transmitsan operation state saved electricity notification command having, as aparameter, a difference between electricity consumption in a normaloperation state and the electricity consumption in the current operationstate, to the TV 50.

The TV 50 receives the operation state saved electricity notificationcommand, and calculates a product of the electricity consumptiondifference shown by the parameter in the command and the transmissiontime interval of the operation state saved electricity request command.The TV 50 adds the product to a value stored in the saved electricityconsumption amount storage unit 503. In this way, the amount of savedelectricity consumption of the DVD recorder 60 is stored in the savedelectricity consumption amount storage unit 503.

In addition, having received the operation state electricity consumptionnotification command and the operation state saved electricitynotification command, the TV 50 displays the current operation state ofthe apparatus transmitting the commands on the screen of the TV 50, asshown by an OSD display 3301 in FIG. 20.

Furthermore, the electricity consumption amount storage unit 502 in theTV 50 stores a pair of a value corresponding to the current day and arecording date and time in the log recording unit in the electricityconsumption amount storage unit 502, at regular time intervals such as24-hour intervals. Having stored the pair of the amount of electricityconsumption for the regular time interval and the recording time in therecording unit in this way, the electricity consumption amount storageunit 502 resets the value in the current-day storage unit in theelectricity consumption amount storage unit 502 to 0.

Note that the time intervals of recording a log of the amount ofelectricity consumption and the amount of saved electricity consumptionare not limited to 24-hour intervals, so long as they are regular timeintervals. Here, the log recording unit records, for example, a logcorresponding to 30 days, and deletes the log in order of occurrencewhen 30 days are exceeded.

Moreover, having received the operation state electricity consumptionnotification command and the operation state saved electricitynotification command, the TV 50 may display not only the operation stateof the apparatus but also the current electricity consumption.

Here, electricity consumption or saved electricity may be displayed,using a numeric value of electricity, a ratio to maximum electricityconsumption in the apparatus, or an icon that changes in proportion tothe numeric value of electricity or the ratio of electricity.

In this way, the TV 50 can obtain the amount of electricity consumptionand the amount of saved electricity consumption of the DVD recorder 60.

The TV 50 can equally obtain the amount of electricity consumption andthe amount of saved electricity consumption of the set-top box 70, as aresult of the transmission of the operation state electricityconsumption request command and the operation state saved electricityrequest command.

(Electricity Consumption Amount Display by the TV 50)

The following describes the case where the user operates the remotecontrol 40 of the TV 50 or a menu of the TV 50 to display an amount ofelectricity consumption and an amount of saved electricity consumption.

First, the TV 50 references the electricity consumption amount storageunit 502 and the saved electricity consumption amount storage unit 503in the TV 50, and obtains electricity consumption amount information andsaved electricity consumption amount information. The TV 50 calculates atotal amount of electricity consumption of the apparatuses, and displaysthe amount of electricity consumption on a daily basis. For example, asshown by the OSD display 2002 in FIG. 12, an amount of electricityconsumption from 30 days ago up to 1 day ago is displayed where ahorizontal axis represents a time and a vertical axis represents anamount of electricity consumption. In the same manner, the TV 50calculates a total amount of saved electricity consumption on a dailybasis and displays it on the screen.

Here, values stored in the electricity consumption amount storage unit502 and the saved electricity consumption amount storage unit 503 in theTV 50 may be added respectively to the displayed amount of electricityconsumption and amount of saved electricity consumption.

Moreover, the amount of electricity consumption and the amount of savedelectricity consumption may be OSD-displayed when the user powers ON theTV 50 and the TV 50 starts video output.

Thus, the amount of electricity consumption and the amount of savedelectricity consumption of the TV 50, the DVD recorder 60, and theset-top box 70 can be displayed to the user.

Note that the power control of each component is not limited to themicrocomputer or the like shown in the above embodiments, and mayinstead be performed by another power control unit that performs onlypower control.

The first and second embodiments describe an example where the TV, as amaster apparatus in the AV system, transmits a control command to theDVD recorder and the set-top box to thereby switch the operation mode ofthe DVD recorder and the set-top box. However, the present invention isnot limited to such, and the DVD recorder or the set-top box may serveas the master in the AV system.

Moreover, the first and second embodiments describe the case where theTV, the DVD recorder, and the set-top box are connected in the AVsystem, but this is not a limit for the present invention. For example,as shown in FIG. 21, the TV 50, an AV amplifier 65, and the set-top box70 may be connected in the AV system. In this case, for example, the AVamplifier 65 has a plurality of operation modes as shown in FIG. 22,where the AV amplifier 65 in a power-OFF state has at least thepower-OFF operation mode 1 and the power-OFF operation mode 2. Thestructures and operations in this case are the same as those in thefirst and second embodiments, and so their description is omitted.

As described above, in the AV system where a plurality of apparatusesthat each have a plurality of operation states of different electricityconsumption are connected via a communication network such as HDMI, theplurality of operation states can be controlled so as to improveelectricity consumption efficiency in the AV system. In detail, supposeone apparatus has the power-OFF operation mode 1 in which the apparatusis in a power-OFF state but a part of the apparatus is supplied withpower, and the power-OFF operation mode 2 in which fewer functions areoperational than in the power-OFF operation mode 1 and thereforeelectricity consumption is lower than the power-OFF operation mode 1.For example, the apparatus which is in the power-OFF operation mode 1switches its operation state to the power-OFF operation mode 2 of lowerelectricity consumption, on the basis of a control command or the likereceived from a master apparatus. Such control contributes to efficientelectricity consumption of the apparatus.

Thus, according to the present invention, an operation state of aconnected apparatus is switched by a control command or the like ofanother apparatus, with it being possible to improve electricityconsumption efficiency. Hence, an electrical power saving system thatachieves efficient electricity consumption of apparatuses connected viaa communication network can be realized.

Note that the TV in the AV system described above is one embodiment of avideo display apparatus capable of displaying video, and the videodisplay apparatus is one particular embodiment of the first apparatusaccording to the present invention. Likewise, each of the DVD recorderand the set-top box is one embodiment of a video recording apparatuscapable of recording and reproducing video, and the video recordingapparatus is one particular embodiment of the second apparatus accordingto the present invention.

Although the electrical power saving system according to the presentinvention has been described by way of the above embodiments, thepresent invention is not limited to the above embodiments. Applyingvarious changes conceivable by a person skilled in the art to theembodiments and combining components in the different embodiments arealso included in the scope of the present invention without departingfrom the principles of the present invention.

The present invention is applicable to an electrical power savingsystem. In particular, the present invention is applicable to anelectrical power saving system, such as an AV system, in which anoperation mode is switched by performing transmission and reception of acontrol command between apparatuses connected via a communicationnetwork.

1. An electrical power saving system comprising a video displayapparatus and at least two video and audio signal transmissionapparatuses that are connected to each other via a communicationnetwork, each of said video and audio signal transmission apparatusesbeing configured to transmit a video and audio signal to said videodisplay apparatus, each of said video and audio signal transmissionapparatuses including: a transmission and reception unit configured totransmit and receive a control command to and from other apparatuses viathe communication network; and an operation state switching unitconfigured to switch between operation states that differ in electricityconsumption, according to the control command, wherein said operationstate switching unit is configured to switch a current operation stateto an operation state of lower electricity consumption, when saidtransmission and reception unit receives a control command indicatingthat another one of said video and audio signal transmission apparatusesis transmitting a video and audio signal to said video displayapparatus.
 2. The electrical power saving system according to claim 1,wherein each of said video and audio signal transmission apparatusesfurther includes a timer unit configured to count an elapse of apredetermined time, and wherein said operation state switching unit isconfigured to switch the current operation state to the operation stateof lower electricity consumption, when said timer unit counts the elapseof the predetermined time in the current operation state.
 3. Theelectrical power saving system according to claim 1, wherein each ofsaid video and audio signal transmission apparatuses further includes: aholding unit configured to hold a state table showing combinations ofoperation states of each of said video and audio signal transmissionapparatuses and said another one of said video and audio signaltransmission apparatuses; a display unit configured to display the statetable to a user; and an input unit configured to allow the user toselect a desired combination from the state table displayed by saiddisplay unit, and wherein said transmission and reception unit isconfigured to transmit a control command to switch the current operationstate according to a selected desired combination of operation states.4. An electrical power saving method of a video display apparatus and atleast two video and audio signal transmission apparatuses connected toeach other via a communication network, each of the video and audiosignal transmission apparatuses including: a transmission and receptionunit that transmits and receives a control command to and from otherapparatuses via the communication network; and an operation stateswitching unit that switches between operation states that differ inelectricity consumption, according to the control command, saidelectrical power saving method comprising: receiving, by thetransmission and reception unit of one of the video and audio signaltransmission apparatuses, a control command indicating that another oneof the video and audio signal transmission apparatuses is transmitting avideo and audio signal to the video display apparatus; and switching, bythe operation state switching unit, a current operation state to anoperation state of lower electricity consumption.
 5. An electrical powersaving system comprising at least a first apparatus, a second apparatus,and a third apparatus that are connected to each other via acommunication network, each of said second apparatus and said thirdapparatus being configured to transmit a video and audio signal to saidfirst apparatus, each of said second apparatus and said third apparatusincluding: a transmission and reception unit configured to transmit andreceive a control command to and from other apparatuses via thecommunication network; and an operation state switching unit configuredto switch between operation states that differ in electricityconsumption, according to the control command, wherein, in said secondapparatus, said operation state switching unit is configured to switch acurrent operation state to an operation state of lower electricityconsumption, when said transmission and reception unit receives acontrol command indicating that said third apparatus is transmitting avideo and audio signal to said first apparatus.
 6. A video and audiosignal transmission apparatus for communicating with a video displayapparatus and another video and audio signal transmission apparatus viaa communication network, said video and audio signal transmissionapparatus comprising: a transmission and reception unit configured totransmit and receive a control command to and from other apparatuses viathe communication network; and an operation state switching unitconfigured to switch between operation states that differ in electricityconsumption, according to the control command, wherein said operationstate switching unit is configured to switch a current operation stateto an operation state of lower electricity consumption, when saidtransmission and reception unit receives a control command indicatingthat another video and audio signal transmission apparatus istransmitting a video and audio signal to the video display apparatus.